A driving circuit of a light emitting diode (LED) including an AC power, a rectifier, a power converter, a waveform sampler, and a control circuit is provided. The AC power provides an AC signal. The rectifier is coupled to the AC power and outputs a driving signal. The power converter is coupled to the rectifier. The power converter includes an LED and outputs a first signal positive correlated with a current passing through the LED. The waveform sampler is coupled between the AC power and the rectifier, and outputs a second signal directly proportional to the AC signal. The control circuit is coupled between the waveform sampler and the power converter, and outputs a control signal to the power converter according to a comparison result between the first signal and the second signal.