The present invention provides a control method and control device for a PFC (Power Factor Correction) circuit. The control method of the PFC circuit includes the following steps that: step S1, whether an PFC circuit in a frequency converter works abnormally is detected after the PFC circuit is turned on, when it is detected the PFC circuit works abnormally, a step S2 is performed; step S2, the PFC circuit is controlled to be switched off, and then a step S3 is performed; step S3, whether the load power of the frequency converter is greater than a preset switch-on power value is detected, if the load power of the frequency converter is greater than the preset switch-on power value, the PFC Circuit is restarted, and the step S1 is repeated. With the control method and control device of theinvention adopted, the power grid voltage abnormal fluctuation resisting capacity and anti-interference capacity of an air-conditioning unit can be enhanced, the frequent start and stop of the unit where the frequency converter is located can be avoided, and the comfort of a user can be improved.