The invention discloses an AC fault ride-through method for a flexible multi-state switch. Under the condition that the flexible multi-state switch has no a transformer, the flexible multi-state switch and the connected AC distribution network are seriously affected by overvoltage and overcurrent caused by a zero-sequence component. The AC fault ride-through method comprises the steps of after anAC fault occurs, determining a fault position and transmitting fault position information to the flexible multi-state switch by using a distribution network line protection device; after the flexiblemulti-state switch receives the fault information, giving a disconnect command to an outgoing breaker of a feeder, connected with the flexible multi-state switch, in a fault supply area; after the outgoing breaker is disconnected, switching a converter, connected with the fault supply area, in the flexible multi-state switch into a passive control operation state from an active control operation state; and processing an internal fault and an external fault separately. According to the AC fault ride-through method for the flexible multi-state switch, the flexible multi-state switch free of thetransformer has AC fault ride-through capability and long-term stable operation of an AC-DC system is ensured.