This paper proposes one power quality evaluation method of the distribution system based on improving radar chart method, aiming at the problem that the weight allocation of the evaluation index is far too subjective or objective in the power quality comprehensive evaluation of the distribution system. The method applies the minimum deviation to calculate the optimal combination weight of each evaluation index. Based on the traditional radar chart, the determination of the angle value between the axes of each index and the selection of the eigenvector are further improved. Firstly, the sector region is used to replace the original triangle region, and the minimum deviation combination weight method is used to calculate the angle between the axes. Secondly, a new eigenvector evaluation function is selected to evaluate the power quality of distribution system. Finally, the feasibility and rationality of the method are verified by the comprehensive evaluation of the power quality of the 10kV distribution system in a steel bar substation. Compared with the traditional radar chart, the improved one solves the problem of information-sharing among the indicators in the traditional radar chart and the multiple evaluation results, making the evaluation results more accurate and reasonable.