The invention discloses an automatic recognition method for ineffective access of an electric energy meter neutral line. The method adopts a power carrier communication mode, the signal transmitting end of a power carrier module transmits carrier signals to an electric energy meter access power side phase line through a single-pole triple-throw switch, the signal receiving end of the power carriermodule is connected with the power-side neutral line to query receiving signals, whether the signal is received is recorded, a DSP control module realizes automatic recognition on ineffective accessof the electric energy meter neutral line according to the record result, and after the system automatically recognizes the ineffective access of the electric energy meter neutral line, an electric energy error detection method under a state of ineffective access of the electric energy meter neutral line is also provided. The power carrier communication method is adopted, the method is simple, therecognition rate is high, safety and reliability are achieved, and equity and justness of the electric energy meter in electric energy metering and trade settlement can be ensured.