The invention discloses and provides a kind of LED phase cut dimming power supply, which comprises AC power supply, phase cut dimmer, LED phase cut dimming power supply and, LED lamp or LED luminaire. The LED phase cut dimming power supply is composed of anti-interference circuit, rectifier circuit I, switching power circuit, rectifier circuit II, dimmer holding current circuit, decompression filter circuit, DC signal amplification circuit, signal conversion circuit, photoelectric coupler, pulse signal amplification circuit, MOS tube, power supply circuit VCC and power supply circuit VDD, which correspond to each and connect with each other adaptively. The input terminal of the anti-interference circuit connects to the output terminal of the phase cut dimmer, and MOS tube or DC TO DC circuit connects to LED lamp or LED luminaire. The invention can be widely used in the field of LED phase cut dimming power supply.