The invention discloses a power transmission line evaluation and diagnosis method, which includes the following steps: (A) acquiring the power data, abnormal power data and environmental data of a power transmission line on the sensing layer, including the voltage, current, electric quantity, power, frequency, power factor, phase, harmonic waves, power voltage loss, power phase failure, electricity theft, temperature, humidity, icing, wind deflection, lightning strike, power transmission tower side wind speed and rainfall, tension, stress, salt density, sag, displacement and acceleration of each node of the power transmission line; (B) transmitting the acquired data to the application layer via a network layer; (C) carrying out fluctuation analysis on the data on the application layer, carrying out evaluation and analysis on the power transmission line according to an analysis result, and remotely monitoring the site of the power transmission line via an Internet fixed port and the IP (Internet Protocol). The invention also discloses a power transmission line evaluation and diagnosis system. The invention realizes on-site monitoring and fault diagnosis on power transmission lines, and not only meets the requirement of remote information management, but also achieves an on-site equipment monitoring extension function.