The utility model relates to a mobile robot mechanism, in particular to a series compensation device inspection robot mechanism based on a differential principle design. The series compensation device inspection robot mechanism comprises a vehicle body, a first stander, driving mechanisms, rotary resetting mechanisms and traveling wheels, wherein each driving mechanism comprises a motor and a differential mechanism each rotary resetting mechanism comprises a spring, a groove and a cam the first stander is hinged with the vehicle body the motor is arranged on the first stander and drives the traveling wheels positioned on two sides of the vehicle body to realize linear motion or steering motion through the differential mechanism the groove is formed in the first stander one end of each spring is connected with the cam which is always positioned in the groove and the other end of each spring is connected with the vehicle body. The driving mechanisms and the rotary resetting mechanisms are arranged at the front end and the rear end of the vehicle body the driving mechanisms drive the traveling wheels through the differential mechanism to realize the linear motion or the steering motion a resetting function is also realized and the series compensation device inspection robot mechanism has a relatively high motion characteristic.