According to the shortcoming of the limited capacity of the master power in the master-slave micro-grid system based on single V/f source, a new master-slave control strategy is presented for isolated power grid operation in the micro-grid. The new strategy uses multiple main power sources based on the core of micro-sources using V/f controllers, and more than one such power source can operate in the micro-grid. The new strategy can operate by itself automatically according to the default margin without telecommunication and it has the adaptive ability to large amount of power change. Matlab/Simulink software is used for simulation and verification, and the correctness and feasibility are verified by the simulation results. The microgrid has good operating characteristics in both grid-connected and islanded operation modes under the proposed strategy. The model provides an effective way for further research on micro-grid operation control.