According to the application of optical fibre communication network in smart substation, this paper analyzes the status and existing problems of the monitoring of GOOSE network link. Based on the electric characteristics of the physical layer and the analysis of the optical receiving power, a fast monitoring method for optical fibre communication link is proposed, and a detailed blocking scheme is given through simplified bus protection case. This method can detect the abnormal link quickly and give the preventive measures in time, which can solve the problem of slow blocking when the communication link is abnormal and improve the reliability of protection.