Index fund is a kind of fund with the principle of fitting the target index and tracking the change of the target index to realize the synchronous growth with the market. Specifically, it can be divided into replicated index funds and enhanced index funds. The former is to completely copy the underlying index, while the latter is to appropriately adjust the weight of individual stocks on the basis of passive investment in order to obtain better returns than the underlying index.

At present, closed-end funds, such as Zhongxing He, Pufeng and Tianyuan, are all enhanced index funds. The index funds in open-end funds include Huaan SSE 180, Tiantong 180, Bo Shi Yufu, Rongtong SZSE 100, E Fund SSE 50, Great Wall Jiutai, Yin Hua-Dow Jones 88, Huaxia 50ETF and Harvest 300.

Among the existing indexes, SSE 50 index funds have obvious blue-chip characteristics and high industry concentration-concentrated in banking, steel, petroleum and petrochemical, which is highly correlated with economic development; Shanghai Stock Exchange 180 Index and Shenzhen Stock Exchange 100 Index respectively reflect the overall situation of Shanghai and Shenzhen stock markets, in addition to FTSE Xinhua Index and Dow Jones 88 Index.

When stocks are used for band operation, it is easy to "earn the index but not make money" because of the deviation between the stock increase and the index increase, so institutional investors often choose index funds for band operation at present.