A method and a system for controlling a rectifier can obtain a predicted switching interval. The method includes steps of: receiving frequency information and line information of a power generator, the line information including a switching point where a voltage or current crosses zero and a switching interval based on the frequency information; obtaining a predicted switching interval according to the frequency information and the line information, and obtaining a feedback signal according to two terminals of at least one component of the rectifier; and switching a switching signal of the rectifier within the predicted switching interval according to the feedback signal.