The invention relates to a method and device for controlling power quality of a distributed generation system, the method obtains a state-of-charge value of a distributed power generation device and obtains a state-of-charge value of the distributed power generation device, the apparent power of the distributed generation device, the reactive power of the grid connection point in the system to which the distributed generation device belongs, the difference between the bus voltage on the generation side and the grid connection point voltage in the system to which the distributed generation device belongs, and the difference between the bus voltage on the load side and the grid connection point voltage; Judging whether it is within the preset range; If not, the distributed generation deviceand the system are stabilized by adjusting the active output and reactive output of the distributed generation device or cutting off part of the load. As the voltage regulator output of the distribution network doe not need to be artificially and mechanically regulate, each parameter of the distributed power generation system can be regulate in real time according to the load condition, the invention has strong real-time performance and can effectively reduce the cost.