A surge current compensating circuit has a compensating current generation unit and a bias unit, for compensating a surge current drawn from a supply power after an output signal of a specific circuit transits. The compensating current generation unit electrically coupled to the output stage of the specific circuit draws a compensating current form the supply power according to the output signal. The compensating current substantially equals to the surge current, and a summation of a current flowing through the output stage of the specific circuit and the compensating current is substantially unchanged regardless whether the output signal transits or not. The bias unit electrically coupled to the compensating current generation unit provides a bias to the compensating current generation unit to receive the compensating current passed through the compensating current generation unit or output the compensating current to the compensating current generation unit.