A robot was designed to clean the dust in the central air conditioning ventilation pipeline based on the telescopic structure of umbrella.The robot was composed of cleaning units and two groups of walking unit, in which the cleaning head of the cleaning unit was automatically adapted to the change of pipeline diameter through a special spring. The walking part was composed of two groups of walking unit and connecting mechanisms. Three groups of umbrella shaped support structure were equally distributed along the circumference of the walking unit. The robot could pass through the vertical pipeline and pipeline diameter change smoothly through the cooperation of the two groups of walking unit. Through the mechanical analysis to the three groups of umbrella support structure, the mathematical formula for selecting the motor model to drive the support structure was obtained.