Stock index is the abbreviation of stock price index. Stock price index, namely stock index, is a reference index compiled by stock exchanges or financial services institutions to indicate changes in the stock market. When the stock price fluctuates, investors will inevitably face market price risks. Therefore, the stock price index can reflect the change of the overall price level of the stock market, and investors can test the effect of their investment and predict the trend of the stock market.

The stock price index is a statistical relative number of stock prices compiled to measure and reflect the overall price level of the stock market and its changing trend. Usually, the average share price or stock market value in the reporting period is compared with the average share price or stock market value in the selected base period, and the ratio of the two times the index value in the base period is the stock price index in the reporting period. When the stock price index rises, it means that the average price level of the stock rises; When the stock price index falls, it means that the average price level of stocks falls; It is a barometer that sensitively reflects the social, political and economic changes of the country (or region) where the market is located.