With the construction of new power system and the reform of transmission and distribution price, the grid investment decision to meet the precise investment demand becomes more and more important. Based on the existing research on optimization of power grid investment decision at home and abroad, this paper proposes a multi-objective power grid investment decision optimization model considering cost, reliability, social cost, etc., and seeks the Pareto solution by multi-objective particle swarm algorithm. In order to solve the problem that the Pareto solutions cannot be compared with each other, this paper proposes to rank the Pareto solutions by game combination assignment and VIKOR method, and then select the optimal investment plan. The correctness of the proposed multi-objective grid investment decision optimization model and the feasibility of the solution and ranking method are verified through the analysis of the calculation cases.