Distributed generation (DG) and its planning are increasingly becoming more important in the power system for its advantages. This paper presents a distributed generation planning strategy based on multi-objective optimization approaches. The main goal of this paper is to determine best location and size of new Distributed Generation units by minimizing different cost functions and considering the technical aspects as constraints. The best planning strategy is determined based on the marginal benefit of each planning scheme among the Pareto set which is obtained by Normal Boundary Intersection algorithm