The present invention relates to an electric energy quality early warning method which is realized through a mean value-standard deviation control chart. The control chart comprises a mean value control chart and a standard deviation control chart. The method comprises the steps of determining the early warning indicator of electric energy quality, judging whether the early warning indicator excesses a standard, preparing the sample group of the historical data of electric energy quality, determining the control limit of a mean value-standard deviation control chart, judging the stability of the data through the sample group through the mean value-standard deviation control chart, judging whether the real-time monitoring data of the electric energy quality is abnormal or not, judging an early warning level according to the abnormal type of the monitoring data, and giving early warning information. According to the invention, the electric energy quality early warning method is used to establish an electric energy quality early warning system, the safety problems or potential problems in a grid are found timely, early warning information is given, the timely adoption of the control measures by an operator is facilitated, the problems are processed as soon so possible or the potential problems are solved in the bud, the grid safety operation and equipment maintenance are served, and the method has a practical meaning for ensuring the reliable operation of a grid.