A synchronous rectifier applied to a power converter includes a power supply module, a control module, and a gate driving unit. The power supply module is used for generating a supply current according to an induced voltage generated from a secondary side of the power converter, wherein the supply current is used for establishing a supply voltage, and the induced voltage corresponds to a control signal of a power switch of a primary side of the power converter. The control module is coupled to the power supply module for turning on or turning off the power supply module according to the supply voltage. The gate driving unit is coupled to the power supply module for generating a gate control signal controlling turning-on and turning-off of a synchronous switch of the secondary side of the power converter, wherein the supply voltage is used for driving the gate driving unit.