Aiming at the power flow control and identification of the main monitoring branch, which are the key problems of electromagnetic loop network by generator tripping measure, a power flow control form based on distribution coefficient and phase angle matching analysis is presented. This control form is based on the conventional distribution coefficient method, eliminates the influence on power flow control caused by the generator tripping through generation shift distribution factors, and according to the DC power flow, identifies the key monitoring line by the matching degree of voltage phase angle of lines with high voltage and low voltage. Example analysis results against the 500/220 kV electromagnetic loop network in the southern province show that the proposed method can avoid overload operation on the low voltage line after the high voltage line of the electromagnetic loop network is disconnected and security measures are taken to remove the unit, thus the transmission capacity of the electromagnetic loop network can be fully enhanced under the premise of system security; moreover, the proposed method does not need too much calculation, only through the phase matching analysis, the main monitoring line of the electromagnetic loop network can be identified accurately. So, the presented way effectively alleviates the workload of scheduling monitoring and has high performance on the safety precaution.