The isomorphism of open-end fund and closed-end fund has become two modes of fund operation. Open-end fund refers to a fund operation mode in which fund sponsors can sell fund shares or shares to investors at any time according to their needs, and can redeem the fund shares or shares issued at the request of investors when setting up the fund. Investors can buy funds through fund sales agencies, so that the assets and scale of the fund will increase accordingly, or they can sell their fund shares to the fund to recover cash, so that the assets and scale of the fund will decrease accordingly.

Monetary fund is an open-end fund that collects idle social funds, is operated by fund managers and kept by fund custodians. It specializes in investing in low-risk money market instruments, which is different from other types of open-end funds. It has the characteristics of high security, high liquidity, stable income and "quasi-savings".