Abstract: Aiming at the cleaning demand of rectangular ventilation pipeline, a cleaning robot for rectangular ventilation pipeline was designed, which was mainly composed of driving mechanism, variable distance mechanism and cleaning mechanism. According to the working conditions of the robot in the vertical pipeline, the static equilibrium equation was constructed to determine the minimum pressure exerted on the robot wheel by the pipe wall. Through the mechanical analysis of the variable distance mechanism, the relevant mathematical model of the variable distance mechanism was established to determine the relationship between the motor torque and the pressure on the wheel. The parametric modeling of variable distance mechanism was carried out by ADAMS, the length of each link rod was taken as design variable, and the geometric constraints were considered. Taking the minimum force of the sliding pair between the slider and the ground as the objective function, the ADAMS built-in algorithm OPTDES-GRG was used to optimize and analyze the variable distance mechanism. The results show that the optimized length of the link rod enables the robot to be used for pipelines with a height of 220-293 mm, and the driving torque is reduced by 45.2% compared with that before optimization.