Abstract: In order to discuss reasonable configuration of voltage grade of micro-grid with distributed generation in medium-term and long-term planning, this paper analyzes mathematic relations between cost of micro-grid and voltage grade, power supply radius, load size, distributed generation capacity and power supply reliability in power supply region from the cost characteristic. According to existing voltage grade sequence of power distribution network, optimization model for structure of multi-voltage grade micro-grid was constructed and taking its minimum cost characteristic function as an objective function, an improved hybrid optimization genetic method was used for selection and optimization on voltage grade of the objective micro-grid. Applications of various voltage grade sequences in micro-grid were compared by means of examples and the best voltage grade sequence of micro-grid with distributed generation in future development was obtained.