Micro-grid is an autonomous system of self-control, protection and management. It can operate both jointly and separately and improve the reliability of power supply to a great extent. This paper provides a multi-stage decision planning method for micro-grid, less time-consuming and easier to solve in comparison with the traditional method, aiming at the promotion of the reliability of power supply of the distribution network. At the first phase, according to the fault traversal influence matrix, a reliability evaluation is implemented on the system to find out the load point which can’t meet the requirement for reliability. At the second phase, the position and number of micro-grid are confirmed by node adjacent matrix on the basis of the load point searched at the first phase. At the third phrase, with the voltage deviation and minimum network loss as the objective functions and calculated by harmony search with global searching ability, the capacity of distributed generation in all micro-grids are defined. In order to improve the stability of the algorithm and avoid falling into local optimum, dynamic memory choice probability and disturbance probability of harmony search are used, changing with the increase of the number of iterations, and the solutions of harmony memory is selected based on crowded degree distance. The effectiveness and rationality of this method are verified by simulation results of RBTS-BUS 6-bus system.