Bond fund is a kind of securities investment fund with bonds as the main investment object. It invests in bonds by pooling the funds of many investors. Bond funds have the characteristics of low risk and stable income, and interest income is the main source of income for bond funds. Bond funds are suitable for investors who pursue stable income. According to the classification standard of China Securities Regulatory Commission, more than 80% of fund assets are invested in bonds. Generally speaking, bond funds can be roughly divided into three categories. Among them, the fund contract stipulates that all funds invest in the bond market (except convertible bonds and convertible bonds that can be traded separately), and such funds are pure debt funds; Non-pure debt funds with fund assets as high as 20% can subscribe for new shares in the primary market are called "primary debt base"; A bond fund that can invest up to 20% of the fund assets in the secondary stock market is called "secondary debt base".