Based on the limits to relevant power quality indices set in national standards， a unified power quality index system is established in the same measuring scale. This paper presents a comprehensive power quality evaluation model based on the radar chart method. First， unified power quality indices are introduced. The weight of each index is determined with the multi-level interactive algorithm. Then an improved radar chart method of the eigenvalue calculating algorithm is applied to the comprehensive evaluation of power quality， in the process of which the information loss due to data naturalization is avoided and the evaluation result is concise， clear and intuitive. Simulation results show that the evaluation method proposed is intuitive and credible and of greater realistic significance.