The invention relates to a dimming circuit and a lamp thereof. The dimming circuit comprises a potentiometer, an NPN type triode, a third resistor, a fourth resistor, a fifth resistor and a voltage stabilization diode. The collector of the NPN type triode is coupled to a node between the base of a PNP type triode and a second electrode, the base of the NPN type triode is coupled to a central tap of the potentiometer, the emitter of the NPN type triode is grounded via the third resistor, one end of the potentiometer is coupled to the cathode of the voltage stabilization diode and one end of the fifth resistor, the other end of the potentiometer is grounded via the fourth resistor, the other end of the fifth resistor is coupled to a load unit, and the anode of the voltage stabilization diode is grounded. Dimming functions are achieved through the simple circuit, and the dimming circuit is simple and reliable in design, low in cost and stable in working, and is applicable to various LEDs.