Reasonable power quality assessment is of great singnificance in reformation of electricity price. Based on data envelopment analysis evaluation method is proposed for comprehensive assessment of the power quality. The indicators deviation of the measured data with the power quality national standard as input index, The assessment grade of power quality as output indicators.By using the data envelopment analysis method to evaluate efficiency of the decision making units , through analyze the unit efficiently between standard unit, get the assessment grade of decision making units.Using data envelopment analysis method to avoid the drawbacks influence of weight selection on the power quality evaluation.By a numerical example, this method can objectively reaction monitoring power quality status.