Fixed investment refers to investing in a designated open-end fund with a fixed amount at a fixed time, similar to the bank's zero deposit and withdrawal method. Fixed investment spreads risks by constantly buying, increasing the number of positions and sharing costs. Investors can manually increase or decrease positions in the process of fixed investment.

For example, when the market is good, investors can lighten their positions and realize part of the income, while when the market is bad, investors can add positions and spread the cost of holding positions evenly through adding positions.