There is a problem of large motion system error of an indoor inspection robot in a substation under complex conditions. This results in narrow coverage of inspection points. This paper proposes a scheme for a cable-driven inspection robot system. We consider the characteristics of the inspection route of the substation, and the system hardware of the inspection robot is designed in detail from the three aspects of the servo drive, motion control and machine vision systems. The system software is designed using motion control and visual system software. A kinematics model of the flexible carrying mechanism is established. A horizontal and vertical fixed-point inspection track simulation is carried out. The demonstration application of a 66 kV substation in the China Southern Power Grid shows that the horizontal and vertical motion errors of the flexible cable-driven inspection robot designed in this paper can be controlled within 0.03 mm. This effectively improves the accuracy of the motion system and has broad application prospect in indoor inspection of substations. This work is supported by the Key Project of National Natural Science Foundation of China (No. 51437003) and the Science and Technology Project of Guangxi Power Grid (No. GXKJXM20180356).