The invention relates to a monitoring method for electric energy quality, which relates to four functions of load phase modulation, on-load capacitance regulation, reactive compensation and on-load voltage regulation, and can strictly judge and execute load phase modulation, on-load capacitance regulation, reactive compensation and on-load voltage regulation in sequence. According to the method, operating parameters and state information of a distribution transformer can be monitored and collected in real time, the reasons of the electric energy quality problem can be comprehensively judged, three phase loads of the distribution transformer can be automatically controlled to be balanced as much as possible, the no load loss of the distribution transformer can be reduced, the power factor is promoted, the voltage quality is improved, a station area of the distribution transformer can be kept in a economic operation state, and therefore, the monitoring on the electric energy quality in the generalized aspect can be realized, and the electric energy supply is improved.