In order to effectively control the operation cost and improve the efficiency of the distribution network, and in response to the in-depth reform of the new round of power system reform, the optimization of the life cycle cost of the regional distribution network has become an important research direction. This paper first analyzes the complex cost structure of the distribution network and screens the key factors that affect the cost with the help of a system dynamics model. The improved Monte Carlo method is used to sample the key impact factors and obtain the distribution factors of the distribution network. Comprehensive sensitivity coefficient of the impact of the entire life cycle cost of the power grid; Secondly, a cost optimization model with the key influence factor on the total life cycle cost of the distribution network as the minimum is established, and a GAACS combination algorithm is proposed to solve the model; Finally, a 10kV distribution network area in a certain province was selected for an example analysis. The results show that economic conditions have the greatest impact on the cost of the distribution network, and areas with poor technical conditions have a greater ability to reduce costs.