The invention provides a light-dimming mechanism applied to an LED (Light Emitting Diode) car lamp reflecting mirror. A bevel gear is connected with a power source and drives a driving rod to drive a transmission rod, so as to drive an adjusting screw to adjust; the adjusting screw is connected with a light-dimming axis of an AFS (Adaptive Front Lighting System) ellipsoid unit; the AFS ellipsoid unit is connected with an LED car lamp to adjust a reflecting angle of the LED car lamp. The device can be used for controlling a lamp light reflecting angle of the car lamp and increasing the degree of freedom and the space distance of a car lamp adjusting system; compared with a traditional adjusting mechanism, the light-dimming mechanism has high assembling commonality and the design freedom degree of the car lamp is great.