Stock market index is a reference index compiled by stock exchanges or financial services institutions to show changes in the stock market, and it is used as an indicator of changes in market prices. Based on this, investors can test the effect of their investment and predict the trend of the stock market. At the same time, the press, company bosses and even political leaders also use this as a reference index to observe and predict the social, political and economic development situation. Due to the complexity and variety of stock index calculation, people often select several representative sample stocks from listed stocks and calculate the average price or index of these sample stocks. Used to indicate the general trend and fluctuation range of stock prices in the whole market. The "Shanghai Composite Index" is compiled by the Shanghai Stock Exchange, with all the stocks listed on the Shanghai Stock Exchange as the calculation range and the circulation disk as the weight. The Shanghai Composite Index reflects the general trend of the Shanghai Stock Exchange market. The Shanghai and Shenzhen stock indexes are the composite indexes of Shanghai and Shenzhen stock exchanges. Shanghai-based index is the index of closed-end funds in Shanghai Stock Exchange. When investing in stock funds, choose to invest when the stock market falls much on a certain day and redeem it when it rises much. There is a certain connection between stock funds and the stock market. When the stock market falls more unilaterally, funds are not spared. There is no correlation formula between fund and stock market.