A new dynamic prediction method of junction temperature of high-power LED using step-down compensation is proposed in this paper. Firstly, the measuring errors of the conventional FVM method are analyzed. Then the reverse current is used to reduce voltage to accelerate the recombination process of photogenerated carriers, and the program-controlled power supply is controlled by LabVIEW to realize the required current waveform. Finally, the effectiveness of this method is verified by comparing with the test results of the conventional method.