To control the electromagnetic interference (EMI) generated by the power sup ply of dimmed light emitting diode (LED) display panels,researches have been finished on the power supply current spectrum of th e panel with three pulse width modulation (PWM) dimming approaches.Firstly,we compare the dimming principles of the linear PWM,the discr ete PWM,the gated PWM,and their potential electromagnetic interference.And then an assessme nt method of electromagnetic interference based on current spectrum analysis is designed,and the validity o f the method is verified by the simulation of the single brightness and the gradually-changed brightness images .Finally,by the current spectrum analysis of an LED panel displayed with real images,we compare the potential interferenc e of the three dimming approaches.Experiment results demonstrate that large interference will be gener ated when LEDs are lighted simultaneously with the linear PWM,and it could be effectively reduced by the e xtension of consumed current and the code compensation effect with the discrete PWM,and the narrower minimu m lighting pulse duration is not in favor of interference reduction with the increment of gating levels used in the gated PWM.The achieved analysis results could be applied to reasonably carry out electromagnetic interf erence analysis and distribution when designing new LED panels,and to forecast the electromagnetic compatibility of the products.