Facing the problem of locating and sizing of distributed generation (DG) in distribution network, a multi-objective optimization model is proposed in this paper. The multi-objective function includes the maximum penetration of DG, maximum system network loss improvement rate and the maximum voltage quality improvement rate and its weight determined by estimation-matrix method. An improved fruit fly optimization algorithm (IFOA) is proposed and employed to optimize the location and sizing of the distributed generation. The simulation results of IEEE 33 node system show that, compared with the genetic algorithm (GA) and traditional fruit fly optimization algorithm (FOA), the improved fruit fly optimization algorithm has a great advantage in search speed and accuracy, which verifies the practicability and validity of the proposed optimization model and improved algorithm.