CSI 500 Index is a sample stock composed of representative small and medium-sized companies in Shanghai and Shenzhen stock markets. Sample stocks of the Shanghai and Shenzhen 300 Index and the top 300 stocks with daily average market value in the latest year are deducted from the sample, and the remaining stocks are sorted from high to low according to the daily average turnover in the latest year (since the listing of new shares), and the bottom 20% stocks are excluded. Then the remaining stocks are sorted from high to low according to the average daily market value, and the top 500 stocks are selected.