The invention belongs to the technical field of LED lamp control and provides a dimming circuit. The dimming circuit comprises a PWM signal output module, a first safety capacitor, a second safety capacitor and a voltage conversion module, wherein output ends of the PWM signal output module are connected to first ends of the safety capacitors; second ends of the safety capacitors are connected toan input end of the voltage conversion module; the PWM signal output module outputs a primary PWM signal to the first safety capacitor; the first safety capacitor isolates the primary PWM signal and then outputs a secondary PWM signal to the voltage conversion module; and the voltage conversion module converts the secondary PWM signal into a dimming voltage feedback signal and transmits the dimming voltage feedback signal to a main control chip through the second safety capacitor. The safety capacitors are arranged between the PWM signal output module and the voltage conversion module for isolation, and a photo-coupler and a transformer for isolation in a traditional dimming circuit are replaced, so that transmission of linear signals can be achieved, and furthermore, the dimming circuit is small in occupied space and low in overall cost.