A synchronized rectification control method for use in a flyback converter is provided. The flyback converter includes a transformer including a secondary winding, a synchronous rectifier switch and a synchronous rectifier controller. The synchronous rectifier switch is coupled to the secondary winding and the synchronous rectifier controller, and is used to output a voltage difference signal and receive a control voltage. The method includes the synchronous rectifier controller detecting a rapid falling edge of the voltage difference signal to generate a rapid falling edge signal, generating an envelope signal according to the voltage difference signal, generating a time length control signal according to the voltage difference signal and the envelope signal, generating a blanking time signal according to the voltage difference signal and the time length control signal, and performing a logic operation on the blanking time signal and the rapid falling edge signal to generate the control voltage.