One of the core objectives of power system operation is to provide high-quality energy, the quality indicators of power system operation are mainly reflected by power quality. In order to assess the power quality objectively and effectively, a comprehensive evaluation method of high-quality network operation based on rough set and evidence theory is proposed. The method applies rough set theory to define the decision-making strength and expansion rules and uses the decision-making table to obtain the basic probability assignment of evidence theory, which make the result of probability assignment more objective. And then by applying the fusion rules of evidence theory to integrate the various indicators of power quality, the pros and cons of ordering from each power quality evaluations can be obtained to achieve a comprehensive evaluation of power quality. The examples show that the results of power quality evaluation are more objective and rational by using this method. So it can prove the correctness and superiority of this method.