The invention provides a synchronous rectification 
control circuit and a control method thereof. The synchronous rectification 
control circuit comprises a threshold detection circuit, a threshold generation circuit, an output 
voltage detection circuit, a 
logic control circuit, a soft-off circuit and a 
signal amplification circuit. The threshold detection circuit samples the 
voltage at the two endsof the drain and the source of the synchronous rectification MOS tube, compares the 
voltage with an internally set threshold and outputs a corresponding 
control signal to the 
logic control circuit; the output voltage detection circuit detects the output voltage, judges whether the output voltage exceeds a preset reference voltage or not, and outputs a 
signal to the 
logic control circuit; the logic 
control circuit processes signals output by the threshold detection circuit and the output voltage detection circuit and outputs a 
control signal to the 
signal amplification circuit, and the signalamplification circuit amplifies the 
control signal and then outputs a synchronous rectification driving signal; and a soft turn-off circuit realizes a soft turn-off function. The synchronous rectification control circuit can enable the primary side detection circuit to be judged easily, and improves the reliability; and the time of 
secondary side current passing through the body 
diode is reduced through soft turn-off, and the synchronous rectification efficiency is improved.