Abstract: Under the driving of rubber sealing cup, pigging and inspecting robots run downwards inside the pipeline, and their stability of dynamic movement has direct effect on the accuracy, precision and safety of pipeline inspection and maintenance. In this paper, the rubber sealing cup and pressure difference drive force of in-pipe robot was taken as the basis. Firstly, the dynamic behaviors were investigated, such as wax scraping and cutting deformation removal. Secondly, an unsteady movement model was established for the operation of pipeline robot. Thirdly, the friction system of rubber sealing cup during scale scraping was built up concisely. Fourthly, the main factors affecting scale scraping and cutting deformation were analyzed by the orthogonal cutting theory. Fifthly, the sealing friction process of rubber sealing cup of in-pipe robot was described. And sixthly, the effect of mechanical parameter variation and rubber materials on wax scraping was studied by means of in-situ observation, e.g. optical microscope and digital image. It provides a guideline for the optimization of intelligent control algorithm and structural design of rubber sealing cup.