Knife coins are one of the copper coins in the Spring and Autumn Period and the Warring States Period. Its shape evolved from farm tools, hand tools and daily utensils-knives in the Spring and Autumn Period. There are different types, according to their nature or shape, including Qi Dao, Jimo Dao, Anyang Dao, Tan Bang Dao, Needle Head Dao, Yan Shou Dao, Ming Dao, Flat Head Dao and Straight Dao. Mainly spread in Qi, Yan, Zhao and other countries during the Spring and Autumn Period and the Warring States Period. Qi Dao is the currency of Qi State. There are three-character knives, four-character knives and six-character knives with the word "Qi" on the coin surface. The three-character knife is "unified law (goods)" and the four-character knife is "legalization of qi" The six-character knife is "the law of enriching the country". "Qi" refers to Linzi, the capital of Qi. There are Jimo Dao, Anyang Dao and Tanbang Dao without the word "Qi" on the coin surface.