The invention relates to a single-stage low-switch-stress and low-output-ripple LED drive circuit comprising an input alternating-current power supply uin, a diode rectifier bridge BD1, a main transformer Tr1, an auxiliary transformer Tr2, a first power MOS switch tube S1, a second power MOS switch tube S2, a first power diode D1, a second power diode D2, a third power diode D3, a fourth power diode D4, a fifth power diode D5, a sixth power diode D6, an electrolytic capacitor C1, a first output capacitor Co1, a second output capacitor Co2, an output filter inductor Lf, and an LED lamp load. The LED drive circuit based on combination of a single-stage AC-DC converter Flyback and an auxiliary converter Forward is constructed, so that high-efficiency, low-voltage-stress, low-output-ripple, and constant current output functions are realized.