There are defects or faults in the inner part of GIS equipment that need to be inspected, the GIS tank body is long and the pipe diameter is small, so it is difficult to check the inner state effectively and enter the inner part for maintenance by manual method.The inner inspection robot of GIS equipment is researehed, and adopts the modular design to realize the functions of flexible mechanical arm, foreign matter cleaning and environmental perception monitoring. According to different workplaces, the corresponding robot function modules can be selected for internal work. In the laboratory, GIS equipment tank is built for functional module experiment verification. The experimental results show that the rotation angle and bending angle of flexible mechanical arm module meet the requirements of GIS internal complex environment operation. The foreign body cleaning module can completely clean up different types of small foreign bodies at the bottom of GIS cavity. The environmental monitoring and sensing module can realize the detection of oxygen, hydrogen sulfide and sulfur dioxide in the tank, and ensure the robot to play its role in 110kV and above GIS equipment.