Improved combination weighting radar chart method is provided and applied in synthetic evaluation of power quality. The optimization model was established based on minimizing the deviation between the vectors of evaluation weights before and after the combination weighting. In the method, the sector area was ranked and the angle of the sector area was distributed by the weighting. Moreover, the diagonal of sector area was employed by using the radar chart as index axes. The unattached weighting of every index was not only reflected by the whole hog, but also the interactant was incarnated. Synthetic evaluation of power quality was completed by the area and girth of the radar chart. Verification results demonstrate the reliability and validity of the method.