With the disintegration of the Bretton Woods system after the Second World War, all western countries have experienced economic stagflation since the early 1970s. Under the double pressure of economic crisis and financial chaos, stock market crises frequently occur, and the stock market experienced the most serious crisis after the war. The Dow Jones index even fell more than 50% in the stock market decline of 1973- 1974. Although institutional investors can avoid the unsystematic risks of the stock market by investing in different stocks, investors are still helpless about the systemic risks of ups and downs because there are no corresponding hedging tools available. People realize that there is no suitable financial instrument to use in the face of the stock market decline.

Considering the urgent market demand at that time, KCBT finally launched the world's first stock index futures product-value line index futures contract, 1982 on February 24th. As soon as the stock index futures were born, they achieved unprecedented success. The value line index futures contract was very active on the day of listing. However, the good times did not last long. As the American Wall Street stock market plunged by nearly 25% in June 2009 1987+ 10/9, which triggered the global financial turmoil, people have listed stock index futures as one of the "culprits" that triggered panic selling. After entering the 1990s, with the recovery and development of the economy and the improvement of the internationalization of the global financial market, investors' investment behavior became more rational, and the development speed of stock index futures became more rapid. Developed countries and some developing countries have successively launched futures trading with their own or local stock indexes as the subject matter.

Second, the function of stock index futures

First, the risk aversion function. The hedging function of stock index futures is realized by hedging, and investors can avoid risks by operating in the opposite direction in the stock market and stock index futures market. The risk of stock market can be divided into two parts: unsystematic risk and systemic risk. Nonsystematic risks can usually be minimized by diversification, while systemic risks are difficult to avoid by diversification. Stock index futures have a short-selling mechanism, and the introduction of stock index futures provides the market with a tool to hedge systemic risks.

Second, the price discovery function. Stock index futures have the function of discovering prices. Through the open and efficient bidding of many investors in the futures market, it is conducive to the formation of a stock price that can better reflect the true value of the stock. The futures market has the function of discovering prices. On the one hand, there are many participants in stock index futures trading, and the price formation contains price expectation information from all parties. On the other hand, stock index futures have the advantages of low transaction cost, high leverage ratio and fast instruction execution. After receiving new market information, investors are more inclined to adjust their positions in the futures market, which also makes the stock index futures price respond to the information faster.

Third, the theoretical research of stock index futures.

3. 1 the impact of stock index futures on the volatility of the spot market

Whether the introduction of stock index futures will affect the volatility of spot market, there are three completely different views in theoretical circles: increasing volatility, keeping unchanged and decreasing volatility. The first view is that the speculative behavior of low-information traders will increase the volatility of the spot market because of its leverage. Cox (1976) believes that the main reason for the increase in volatility is the existence of a large number of unsuspecting traders in financial derivatives. Similarly, Finglewski( 198 1) also thinks that futures traders have less information than spot traders, which will increase the volatility of the spot market. The second view is that futures trading has the function of price discovery, which reduces the volatility of the spot market. Bowles (1970) pointed out that the futures market has improved the depth and information of the overall financial market. Dan Hinch (1978) pointed out that futures trading increases the market depth and reduces the volatility of the spot market. However, the mainstream view is that the introduction of stock index futures has not led to an increase in the volatility of the spot market. According to the statistics of Charles M.S. Sutcliffe (1997), among all 43 research conclusions, 25 conclusions have the same volatility, accounting for 58.14% of all conclusions; There are 7 results of volatility reduction, accounting for16.28% of all conclusions; The result of the increase in volatility is 1 1, accounting for 25.58% of all conclusions.

3.2 the impact of stock index futures on the liquidity of the spot market

The introduction of stock index futures has both positive and negative effects on the amount of funds in the spot market. On the one hand, there is a certain substitution effect between stock index futures and stock spot, and the introduction of stock index futures may reduce the liquidity of the spot market. On the other hand, the introduction of stock index futures will promote active trading and reasonable price fluctuation in the stock market. Arbitrage and hedging demand will cause incremental funds to enter the market, which may improve the liquidity of the spot market.

The empirical study of American stock market by Kuserk and Cocke( 1994) shows that after the stock index futures trading, the size and liquidity of the stock market have been greatly improved, and the trading volume of the stock index futures market and the basic spot market has been promoted in both directions. Although the market size of stock index futures may exceed the spot market, it is caused by a large inflow of OTC funds, which has a long-term promotion effect on stock market liquidity. Damodaran et al. A 1. (1990) The empirical study on sample stocks of S & P500 index shows that the introduction of stock index futures has promoted the trading activity of index stocks and improved the liquidity of individual stocks in the five years after stock index futures trading. Most empirical results on liquidity show that, although there is a phenomenon of transaction transfer in the stock market at the initial stage of the introduction of stock index futures, in the long run, the trading volume of both spot market and futures market has increased significantly.

Fourth, the significance of launching stock index futures and the problems that need attention.

4. 1 The significance of stock index futures to the capital market;

First, the introduction of stock index futures will change the capital market structure of China. In the international capital market, stock index futures is the most widely used risk management tool in asset management business. Generally speaking, for systemic risks, it is necessary to hedge risks, and stock index futures are very good hedging tools.

Second, the introduction of stock index futures will change the market trading strategy. This change in the capital market structure caused by the introduction of stock index futures will inevitably lead to changes in investors' trading psychology and behavior. Some investors try to arbitrage between stock index futures and spot market; Some investors will try to profit from the long or short trading of stock index futures; Some investors will try to hedge the risk between stock index futures and spot, so as to realize the expectation of preserving their assets.

Third, stock index futures will change the investor group structure. With the arrival of stock index futures trading, a large number of traders will flood into the capital market, including speculators, hedgers and arbitrageurs. As a new financial derivative, stock index futures do not hinder the investment and participation of retail investors, but from the perspective of speculation or hedging, institutional investors have unparalleled advantages for small retail investors, which means that stock index futures itself is a variety that is more conducive to institutional investors to participate in transactions, providing greater development space for this group.

4.2 China's stock index futures trading needs attention

We can learn from the successful international experience, formulate a series of risk control measures, and strengthen the supervision of stock index futures, so as to facilitate the development of China's capital market and the needs of opening up.

First, design stock index futures contracts scientifically and reasonably. In order to ensure that the function of stock index futures contract is not manipulated, we must first choose the appropriate stock index futures index.

Second, establish a strict risk management system. A strict risk management system should be established in accordance with international practice. In account management, members must be required to open special fund accounts in settlement banks to strengthen risk control. In the settlement system, margin and daily risk-free settlement system are adopted. Investors must pay enough margin before trading, settle the profit and loss of stock index futures trading after closing, and allocate funds at one time. At the same time, establish risk management systems such as market access, daily debt-free settlement, large position report, market inspection, forced liquidation and risk reserve, and adopt advanced risk real-time monitoring technology to prevent and control market risks of stock index futures.

Third, break the barriers between the securities market and the futures market. The mixed operation of financial industry is the development trend of the current international market. At present, in the international financial market, institutional investors vigorously develop investment banking business, and can make effective investment portfolio among futures market, securities market and other markets. However, the futures market in China is isolated from the securities market. For example, financial institutions are not allowed to provide financing or guarantee for futures trading, which is not conducive to institutional investors to carry out stock index futures.