Abstract: In recent years, along with increasing global concerns for environmental protection and energy saving issues, Distributed Generation (DG) technology has become a hot topic. After DG is connected into the distribution network, its structure and operation would be tremendous changed. Therefore, it is of practical significance to study the influence and maximum capacity of DG integration on the distribution network. This paper firstly analyzes the influence on voltage quality of distribution network after DG integration, and proposes an optimization model of DG limit access capacity. The model takes the voltage deviation, voltage fluctuation, short circuit current, line load flow, tidal current equation constraint and distributed force constraint into consideration. Then the distribution network limit capability is calculated using PSO algorithm. Finally, the simulation and optimization result shows that the proposed model and algorithm are effective.