For the problems of uneven accuracy of current distribution between master and slave modules in parallel DC-DC switching power supplies and poor dynamic performance and stability in the face of load disturbances, a control strategy based onthe parallel connection of master-slave current sharing was proposed, combining fractional-order PID with predictive function control (PFC). The prediction function algorithm was improved from the following aspects. Firstly, a piece-wise affine modeling (PWA) of BUCK converter was carried out by using v-step discrete method. Secondly,a new quadratic indicator function was obtained by introducing the idea of fractional-order PID based on the retained predictive function control. Finally, the output effect was compared with that of the conventional PI control. MATLAB simulation was used to test the feasibility and reliability of the fractional order prediction function(FOPID-PFC) control strategy. The simulation results showed that the proposed fractional-order PID prediction function is better than the traditional PI in the accuracy of current sharing, and the overshoot and regulation time were reduced by 234mv, 170μs and 221mv, 210μs, respectively, in the case of load addition and load reduction. Therefore, it is verified that the overall performance of the fractional-order prediction function control strategy based on master-slave current sharing is superior to the traditional PI control in BUCK converter parallel system, and the current allocation accuracy of master-slave module also meets the expected assumption.