A comprehensive optimization model of distribution network is established which takes active power loss minimization as the optimization objective and network topology as constraint conditions，under considering the voltage quality of distribution network and the capacity limitation of reactive power compensation equipment． According to the characteristics of particle swarm algorithm ( PSO) ，that is，premature phenomenon，slow convergence and easily getting the local optimal solution，a particle swarm algorithm based on backtracking iteration ( BPSO) is proposed． The algorithm adopts the "0 － 1" characteristic of backtracking iteration，avoids the invalid search by pruning function in the process of optimization，and improves the optimization path，thus the global optimization performance of PSO is improved． The simulation of IEEE 30 node distribution network example verifies the optimal solution of BPSO algorithm，and the comparison results with the conventional PSO algorithm show the superiority of the proposed algorithm．