Abstract: The optimal configuration of location and capacity of the distributed generation(DG) can widen its technical and economic utilization. Based on the detailed analysis on the characteristics of DG, a model is built to minimize active power loss cost and investment cost. In terms of the defects of traditional firefly algorithm which has such characteristics as easy premature, slow convergence speed and excessive dependence on control parameters, a kind of modified multi-objective firefly algorithm is proposed in this paper by integrating Chaotic search method into firefly algorithm. In order to overcome the disadvantage that the algorithm depends strongly on control parameters, the parameters of firefly algorithm can be adjusted by using the randomness, ergodicity and regularity of the chaos theory. In the end, taking PG & E 69-node distribution network as an example, the Matlab software is used to verify the effectiveness of modified firefly algorithm to locate DG optimally. Results show that it has higher optimization precision and better optimization results than particle swarm optimization(PSO) algorithm and conventional firefly Algorithm.