Abstract: When the passive wireless temperature measurement system monitors the terminal temperature, the installation method of placing the temperature acquisition module inside the terminal main insulation is adopted, which will lead to the electric field distortion of the terminal main insulation. In order to reduce the influence of passive wireless temperature measurement device installed inside the main insulation of the terminal on the main insulation performance, this paper uses COMSOL Multiphysics multi-physics simulation software to establish a simulation model of 320 kV high-voltage DC cable terminal, and studies the terminal temperature monitoring method. Firstly, the problem that the built-in temperature acquisition module will cause the terminal electric field distortion is simulated and verified. In order to reduce the electric field distortion of the cable terminal, the installation method of the temperature acquisition module close to the outer diameter of the main insulation of the terminal is proposed. Secondly, the relationship between the maximum steady-state current carrying capacity of the terminal and the outer diameter temperature of the main insulation of the terminal is studied under different ambient temperatures. Through data analysis, a method for diagnosing the heating state of the cable terminal based on the outer diameter temperature of the main insulation of the terminal is proposed. Finally, the terminal thermal field model is used to verify the feasibility of the proposed diagnosis method, which can be used for the diagnosis of cable terminal fault state.