A PWM-based (pulse width modulation-based) overcurrent protection circuit and an operating method for the same are provided. The PWM-based overcurrent protection circuit includes a pulse-width-modulation circuit that is connected to a charge pump and a load detection circuit of a power-switch circuit. The charge pump outputs a voltage to the power-switch circuit according to a clock-voltage signal. The load detection circuit is used to detect an overcurrent flowing through the power-switch circuit according to a load at an output end of the power-switch circuit. Thus, when the load detection circuit detects the overcurrent, the pulse-width-modulation circuit controls a duty-cycle width of the charge pump, so as to suppress the voltage outputted by the charge pump. Therefore, an output voltage from the power-switch circuit can be corrected for preventing or reducing the overcurrent.