The invention relates to a voltage sag source positioning method with association analysis and electric power calculation being combined. The method comprises the following steps: 1) collecting voltage sag data at power quality monitoring points; 2) analyzing the voltage sag data to obtain a suspected voltage sag source set; 3) establishing an electric power calculation model by utilizing power grid parameters, and establishing a voltage sag source with the reference of the suspected voltage sag source set and calculating voltage result at each node; and 4) comparing the electric power calculation result with the voltage sag data to obtain the voltage sag source. According to the voltage sag source positioning method with association analysis and electric power calculation being combined, the existing data collected at the power quality monitoring points is utilized to carry out analysis, and the voltage sag source is obtained; and then, the suspected voltage sag source is verified by utilizing the electric power calculation, thereby effectively eliminating errors produced in data analysis and improving the accuracy of the result.