The invention relates to a fuzzy comprehensive evaluation method for voltage sag loss risk of a wafer manufacturing enterprise. The method considers the diversity of losses caused by voltage sag to a wafer manufacturing enterprise, and classifies and quantifies direct loss risk and loss risk difficult to quantify caused by the voltage sag. Then according to the quantification result of the loss risk of the voltage sag of the wafer manufacturing enterprise, on the basis of the characteristic of multi-level multi-index loss risk of factory enterprises, a voltage sag loss risk fuzzy comprehensive evaluation system is established to determine the comprehensive loss risk level of the wafer manufacturing enterprise. The method can comprehensively evaluate the situation of loss risk caused by sag to a user.