Reactive power optimization in distributed network with distributed generation is a complex nonlinear optimization problem.In this paper,the improved particle swarm optimization algorithm is used for the reactive power optimization of distribution network.The optimization model is established with the minimum system loss and average deviation of voltage as the objective function and the node voltage and capacitor switching capacity as the constraints.The position variance is introduced into the particle swarm optimization to prevent the particle swarm algorithm from falling into the local optimal solution.The particle is mutated according to the fitness value of the particle in the population,and the performance of algorithm is improved on the basis of guaranteeing the convergence speed of the algorithm.IEEE14 node distribution system with distributed generation as an example is simulated,the results demonstrate that distributed generation can enhance the stability of the power grid and the algorithm has better optimization performance.