The invention provides a travel trailer rearview mirror adjusting system which comprises a detection mechanism, an electronic control unit ECU and an execution mechanism. The detection mechanism detects signals of the vehicle speed, the rotating angle of a steering wheel, the rotating angles of rearview mirrors and resistance change of an angle measurement device in the vehicle reversing process and sends the detected signals to the ECU; and the angle measurement device is installed in the connecting position of a ball pin hook and a sleeve of a motor tractor and a motor home and used for detecting a hinging angle signal. The ECU calculates the hinging angle of the hinging position of the motor tractor and the motor home according to the resistance change signal of the angle measurement device, calculates the rotating angle deflection amount needed by the rearview mirrors at the next moment according to the hinging angle signal, the steering wheel rotating angle signal, the current rearview mirror rotating angle signal and the vehicle speed signal, and controls the deflection amount of the rearview mirrors through the execution mechanism. The angle measurement device is simple in structure and easy to install, and a vehicle reversing view dead zone in the travel trailer reversing process can be eliminated when the angle measurement device is used in the travel trailer reversingprocess. No sensor is needed for the part of the angle measurement device, cost is low, installation is convenient, and the hinging angle can be obtained accurately.