Abstract: External force damage will have an important impact on the transmission line. It is of great significance to accurately grasp the operation of transmission lines in real time,but the traditional transmission line monitoring system has shortcomings. The principle of radar is applied to the transmission line monitoring system,and a new transmission line monitoring system is designed. Firstly,it analyzes many shortcomings of the traditional transmission line anti external force damage system and explains them in detail.Secondly,based on the traditional transmission line monitoring system,it makes a scientific modular design,from the video image collecting unit,intelligent monitoring and warning system of master station extension function the description and interpretation of performance parameters. Finally,the system designed conducted a field test and application in three aspects: human target detection,large machinery detection,and impurity detection. The results show that the system has good practicability and expansibility.