Fixed investment is the abbreviation of fixed investment fund, which means to invest a fixed amount in a fixed fund at regular intervals. With the fixed investment of the fund, investors do not need to choose the opportunity to enter the market from time to time, but only need to set the amount, investment time and target of each investment in advance, and then invest on time as planned, and can also apply for suspension or redemption at any time during the period. The principle of making money by fixed investment is to share the cost equally by using the average cost method, and to make money by persisting in fixed investment for a long time and using the effect of time compound interest. The fixed investment of the fund has the characteristics of low participation threshold, convenient operation, diversified risks and flexible investment, which avoids the difficulties of individual investors in choosing stocks and timing when investing in the stock market, and also avoids the problems of lack of professional knowledge or limited funds.