A circuit protection device and a protection method thereof are provided. The circuit protection device includes a pulse width modulation unit which detects in order for a plurality of current phase of a plurality of transistors. The pulse width modulation unit decides the current phase of the transistors override a first threshold value whether. Then, the pulse width modulation unit sends a control signal to close the transistor that the current phase exceeds the first threshold value, so as to avoid the transistor burn down.