A new type of series resonant Buck-Boost DC-DC converter topology is developed. The full bridge structure is used to generate the voltage square wave. AC current in the LC series circuit is produced through the parallel double series resonant LC network. The stable DC voltage is output by the level clamping network and the voltage regulating range becomes wider by the premise of low switching loss. With the frequency control， problems of high loss and temperature caused by the non-uniform of switch on and off time are avoided. MATLAB simulation and experimental results validate the correctness of the proposed topology.