In order to effectively clean gunpowder residue inside the barrel with different diameters, a barrel scrubbing robot with adjustable variable diameter moving mechanism was designed, and the mechanical properties of the barrel scrubbing robot in the pipeline were analyzed. According to the required functional requirements and performance indicators, the working principle and structure scheme of the robot are determined; the driving mechanism, walking mechanism and cleaning brush of the robot are designed; the mechanical modeling of the force on the robot in the pipeline is carried out based on the D'Alembert principle; the resistance of the cleaning brush, the anti-skid and tension of the walking mechanism and the driving force of the robot are analyzed through simulation. The simulation results show that the barrel scrubbing robot can work stably in the range of 104 to 155 mm without rifling, and the design scheme is feasible.