An extensible switching power circuit includes a plurality of switching power modules and a plurality of synchronous signal generators. Every two adjacent switching power modules are connected through a synchronous signal generator. The switching power modules generate induction electric potentials. Each synchronous pulse generator measures relevant electric potentials of the previous switching power module connected thereto and generates corresponding synchronous signals sent to the subsequent switching power module connected thereto. The subsequent switching power module regulates the phase of its induction electric potential according to the synchronous signals, such that the induction electric potentials of the two adjacent switching power modules compensate each other's energy gaps.