With the increasing popularity and application of intelligent wave recorders, there is a problem that needs to be solved. The problem is that the existing monitoring methods cannot effectively monitor the transient data sampled by the relay protection device. Also the online monitoring capability of the sampling circuit of the relay protection device can be improved. So a method which compares the same type of transient state of intelligent wave recorders based on the effective value of the difference is proposed. First, the sudden variable search method is used to accurately match multiple recording files collected by intelligent wave recorders and protection devices over a certain period of time. Then the transient data is extracted from multiple recording files. Consistent transient data alignment is achieved using waveforms. Finally, from the effective value of the difference calculated by the transient data, the data is accurately compared to achieve monitoring and early warning of the sampling loop. The proposed transient homology comparison technology fits the actual project. The intelligent wave recorder effectively monitors and warns the sampling value of the relay protection device in real time. In addition, it improves the real-time monitoring ability of the sampling circuit, and ensures the safe and stable operation of the power grid. This work is supported by the National Natural Science Foundation of China (No. 51877090).