Based on the analysis of the existing channel fault diagnosis method of fiber pilot relay protection, and within the realization of the physical link and communication state monitoring method in the relay protection and communication interface device, online diagnosis for the channel state of fiber pilot relay protection and communication equipment can be realized in case of not need to plug optical fiber, cable or adding redundant monitoring equipment, and can display the fiber channel real-time status, such as transceiver power and error code, etc. When a fault occurs in the channel, real-time status report to operation and maintenance personnel can be shown through the view of the relay protection of LCD, with which channel fault points and fault reasons can be accurately positioned. At the same time, by setting up the channel state of alarm value, the safe operation of hidden trouble for fiber pilot protection because of channel failure problem can be detected and solved early.