At present, the stock indexes in the market, whether composite index or component index, only represent the respective market trends of the two markets, and neither of them has the ability to reflect the overall trend of the Shanghai and Shenzhen markets. The Shanghai and Shenzhen 300 Index is a "barometer" reflecting the overall trend of the Shanghai and Shenzhen markets. The index sample is selected from Shanghai and Shenzhen stock markets, covering most of the circulating market value. Component stocks are mainstream investment stocks with good market representation, high liquidity and active market transactions, which can reflect the income of mainstream investment in the market.