A method capable of sensing a heavy load and a short circuit of a low dropout regulator includes providing a ramp pulse signal to the low dropout regulator, providing a square waveform, comparing a feedback signal of the low dropout regulator with the square waveform, and determining the low dropout regulator is a heavy load or a short circuit if a duration that the feedback signal is greater than a low voltage level of the square waveform and lower than a high voltage level of the square waveform is not greater than a pulse width of the square waveform. The method includes determining the low dropout regulator is a light load if the duration that the feedback signal is greater than the low voltage level of the square waveform and lower than the high voltage level of the square waveform is greater than the pulse width of the square waveform.