The invention provides a static frequency converter system and a switching method from intermittent commutation to natural commutation. The switching method comprises the following steps of: when themotor stator frequency reaches a set switching frequency threshold, locking a machine side inverter module in a frequency converter, and controlling the work of a network side rectifier module in an inversion state; detecting a current of a motor stator, when the current of the motor stator in a set time quantum is still smaller than or equal to a set current lower threshold, locking the network side rectifier module until a thyristor in the network side rectifier module to be switched off; controlling the network side rectifier module to be worked in a rectification state to control the machine side inversion module to be worked in a natural commutation mode. According to the technical scheme of the invention, the motor is smoothly converted from an intermittent commutation phase to a natural commutation phase, and the phenomenon of commutation failure does not occur during the switching process.