The invention relates to a dimming circuit of LED lamp, including a constant voltage source, a switching tube connected in series with the LED load at the output end of the constant voltage source, a short circuit detecting circuit electrically connected with the constant voltage source, and an signal processing circuit electrically connected with the output end of the short circuit detecting circuit, and driving circuit respectively connected to the output end of the signal processing circuit and the switching tube, wherein the signal processing circuit calculates whether the short circuit condition is determined, and the timing control detects the LED load short circuit recovery in the event of a short circuit. The driving circuit drives the switching tube to be turned on or off according to the control signal of the signal processing circuit under normal conditions to perform PWM dimming on the LED load, and in the case of a short circuit, the switching tube is turned off to achieve short circuit protection, and In the case of short circuit elimination of LED load, drive the switching tube to conduct temporarily to detect recovery. The dimming circuit of the LED lamp has a short circuit response speed and a good protection effect.