Abstract Robot technology has been successfully applied to the internal inspection of large power transformers. In order to further improve the level of robot intelligent control and realize robot motion control accuracy of the floating state, this paper analyzes the factors that affect the jet thrust of the robot propulsion system on the developed spherical transformer internal inspection robot platform based on jet propulsion, and builds an experimental platform. Combining experimental data to establish jet thrust equation. On this basis, the working state of the robot power system is further analyzed, the equivalent discharge model of the robot battery is established, the battery state parameters are introduced into the jet thrust equation. Finally, a mathematical model of jet thrust prediction is established that comprehensively considers the robot power system, control system, and environmental parameters. The establishment of this model lays a good theoretical foundation for the establishment of the robot’s precise dynamics model, fine motion control and intelligent control algorithm.