The invention provides a system for evaluating the transmission performance of electric power backbone OTN. The system comprises an overhead line structure sensor, station collectors, a plurality of optical cable line collectors located between adjacent stations, a plurality of regional servers connected with a cloud platform and a plurality of functional servers, the overhead line structure sensor uploads collected information to the nearby optical cable line collector through a wireless network, each station collector receives the information sent by the nearby optical cable line collector through the wireless network and communicates with the corresponding OTN device through a network cable, and each regional server exchanges information with the station collection within a corresponding region through an information intranet. The invention further provides an evaluation method. According to the system and method provided by the invention, the evaluation device is firmly combined with the OTN transmission line, and the fault position and fault type can be automatically judged, thereby greatly improving the evaluation efficiency and evaluation quality of OTN transmission performance, reinforcing the controllability of the electric power backbone OTN transmission system and realizing the intelligence of the transmission system.