1. In the study of Wan Tao in the Western Zhou Dynasty, it was put forward that "Wan Tao in the Western Zhou Dynasty was an early calculation tool" and "There was an original abacus calculation in the Western Zhou Dynasty". The historical age of ancient abacus was advanced by 1000 years, and abacus existed in China around 1000 BC, with a history of more than 3,000 years, which had a great influence in international academic circles.

2. Based on the in-depth study of Notes on Arithmetic, 13 kinds of recovery diagrams of computing tools recorded in Notes on Arithmetic (called "Li Imagination Diagram" in abacus circles) are put forward, and recovery models are made and exhibited in the Computing Instrument Exhibition Hall of Inner Mongolia Normal University and Nantong Abacus Museum. He also proposed that "Jiugong Calculation" was the only non-position calculation tool in ancient China, which had the function of expressing infinite quantity, and was a unique viewpoint. He initiated a seminar on "numerology notes", which attracted the attention of abacus circles.

3. Cheng Dawei and Wang Wensu, abacus experts in Ming Dynasty, made great achievements. He found out the origin and date of birth and death of Cheng Dawei from Cheng's genealogy, which was regarded as a great contribution by mathematical historians. He proposed that Wang Wensu's Arithmetic Collection was the first abacus book in China, which made Wang Wensu's works highlight the historical value. He proposed to commemorate the symposium of Cheng Dawei and Wang Wensu, and establish a memorial hall for Cheng Dawei and Wang Wensu. With the support of the local government, memorial halls were established in their hometown of Huangshan City and Fenyang City, becoming famous tourist attractions and patriotic education bases. He put forward many new ideas on the study of Cheng Dawei and Wang Wensu's works, which set off the climax of the study of abacus history in China. Japanese experts in abacus history Suzuki Jiu Nan and Totani Kiichi both participated and sent more than 50 delegations to commemorate Cheng Dawei, which became a temporary victory.

4. The history of abacus algorithm is deeply discussed. We have carefully studied the ancient arithmetic books such as Xiahou Yang's Calculation Classics, Yang Hui's Algorithm, Ding Ju's Algorithm, Arithmetic Enlightenment, Detailed Explanation of Arithmetic, Arithmetic All-round Set, Arithmetic Treasure, Arithmetic New Theory, Arithmetic Unification and Arithmetic Sea Details, and studied the historical evolution of abacus calculation. It is pointed out that the climax of an algorithm in the mid-Tang Dynasty is due to the emergence of an abacus for crossing beams. This view laid a theoretical foundation for "the establishment of abacus in the Tang Dynasty", and thus created an academic view of "the establishment of abacus in the Tang Dynasty", which attracted wide attention from historians. His research on the evolutionary history of agile multiplication and division and reduction division in Yang Hui algorithm; Research on the "clearing" algorithm for calculating the multiplication in the sea: the discovery of formula positioning method in the detailed algorithm: China's demonstration of abacus with diamond beads is a contribution to the study of abacus history.

5. Actively participate in academic activities of abacus history research, and promote the research of abacus history in China. He was a member of the academic activity group of abacus history of the first China abacus association (* * * three people, Yan Dunjie and Hua Yinchun died). One of the founders of China Abacus History Research Association and Shaanxi Mathematics History Research Association. He has been the organizer and host of previous academic seminars on abacus history (* * * ten times). He has participated in academic conferences at home and abroad for many times, and was the only one who published a paper on the history of abacus, the first academic conference on the history of Chinese mathematics held in198/. 1987 and 1993 went to Japan to attend the international conference on the history of mathematics and abacus, and gave academic reports in Tokyo, Osaka and Kyoto, which were warmly welcomed by the Japanese abacus history society. He was elected as the operation committee member of Japan abacus history society. 199 1 taught the history of abacus in CCTV and china national radio, which had a great influence. In 2002, he attended the 24th International Congress of Mathematicians (ICM) and published a research paper on the history of Chinese mathematics.

6. There are many books on abacus and abacus history, and he is a leading figure in the study of abacus history in China. He has published more than 100 papers on the history of abacus and mathematics, and Japan 1 1. His academic paper on reporting in Japan was published in the academic journal On Politics and Economy of the National Academy of Sciences. Writer of Encyclopedia of China, editor-in-chief of Dictionary of Mathematics, deputy editor-in-chief of Biography of Modern Mathematicians in China (multi-volume set), editor-in-chief of Chinese Mathematical History Department, editor-in-chief of Abacus History Newsletter, editor-in-chief of Abacus Magazine and consultant of Abacus and Abacus Mental Arithmetic Magazine. Co-edited the first large-scale abacus dictionary in China (1990) with Mr. Hua Yinchun, a famous expert in abacus calculation in China (1896— 1990), and cooperated with Professor Suzuki Jiu Nan (65438+), a famous expert in the history of abacus calculation in Japan, whose representative works are Calculations. Among them, "Compilation and Interpretation of Algorithms" was awarded as an excellent scientific and technological book in China.

7. The concept of "positive and negative permutation" was founded, which successfully solved the combinatorial mathematics problem of "three constants and six changes" and extended it to the problem of "n constants and k changes", which attracted the attention of combinatorial mathematics.

8. In recent years, important achievements have been made in the study of the history of Xixia, including the publication of the genealogy of Li in Xixia (1998) and the publication of four papers such as Textual Research on the Descendants of Xixia Royal Family. He was invited to attend the international symposium on Xixia studies twice and published academic papers at the conference.

Li is an outstanding teacher and scientist in Shaanxi Province. The thesis won the first prize of excellent thesis of China Abacus Association, and won the excellent thesis prize at or above the provincial level for 6 times. His achievements have been included in Who's Who of Experts in the History of Mathematics in the World, A Dictionary of World Characters and China Dictionary of Modern Mathematicians.