Aiming at the problem for reverse polarity of input and output voltage in traditional multi-inputs converter, and complex structure in the distributed energy collection, a new multiple-inputs Buck-Boost converter is proposed for building DC micro-grid, which wind-solar hybrid power supply is effectively realized, battery is embedded in converter directly, so the volume can be reduced and the cost is lower. It has many advantages, such as simple circuit topology, Boost and Buck, the same polarity of input and output voltage, and the power supply of input source alone or simultaneously, and the battery absorbs or releases power according to the changes of load. A three-input Buck-Boost DC/DC converter is analyzed for its operating modes, input/output characteristics were derived, and DC link power level control is proposed to energy management. The experiment results on Matlab/Simulink platform verify the feasibility of theoretical analysis and the correctness of new control strategy.