The invention discloses an MMC AC fault crossing control method based on a quasi-proportional resonance controller. By controlling the bridge arm current and adjusting the DC side current and AC sidecurrent of the converter at the same time, According to the equalization control of sub-module capacitance voltage, the N sub-module capacitance voltages in one bridge arm of the converter are sortedfrom small to large. If the bridge arm current charges a sub-module capacitor, several sub-modules with lower capacitance voltage are put into operation, and the sub-modules with higher capacitance voltage are removed. If the bridge arm current discharges the sub-module capacitor, several sub-modules with higher capacitance voltage are put into operation, and the sub-module with lower capacitancevoltage is removed. The invention effectively simplifies the upper structure of the MMC controller, reduces the number of the controllers and the control parameters to be adjusted, and is convenient for engineering application.