Comprehensive evaluation of power quality is very important for the governance of power quality issues and the "quality-based pricing" in the power market environment; however

in the existing methods

the change process and trend information on power quality indicators are rarely taken into consideration

and the massive monitoring data accumulated by the power quality monitoring system are not fully utilized

thus it is difficult to reflect the overall situation of power quality over a long period of time. Therefore

on the basis of fuzzy comprehensive evaluation

we introduced data envelopment analysis（DEA）

established a comprehensive evaluation model of power quality on a long-term scale

and put forward the concept of "comprehensive deviation degree of power quality"

which directly reflects the deviation degree and trend information about power quality. Finally

a case study show that the proposed method can be used to obtain the comprehensive evaluation results on a long-time scale

and to reflect the overall situation and trend information of power quality monitoring data.