After the underground drainage pipeline is used for a long time, the dirt and impurities will form silt deposition in the pipeline, causing blockage, which needs to be cleaned in time to maintain the normal operation of the underground pipe network. The current dredging work often requires manual assistance or the cooperation of multiple equipment, the efficiency is not high, and is affected by the size of the inspection well wellhead, the complex environment inside the pipeline and the existence of flammable, explosive, toxic and harmful gases and other factors, making the pipeline dredging work more difficult. Aiming at the present situation and problems existing in the dredging process of large underground drainage pipeline in the city, this design puts forward the conceptual design scheme of pipeline dredging equipment that can be adjusted in diameter, and completes the prototype architecture from four aspects: power system, monitoring system, dredging system and walking system. The design scheme adopts a parallel mechanical mechanism, which can enter the inside of the pipeline from the inspection wellhead with a diameter of 600mm during contraction, and can advance in the inner wall of the pipeline with a diameter of 900-1300mm during extension. At the same time, the sludge is stirred and diluted by a rotating cutter head, pumped out of the pipeline, and the pipeline cleaning is completed after the dredging. The design of this pipeline dredging concept equipment can enter the pipeline from the inspection wellhead, adapt to the work of different pipe diameters after expansion, have the advantages of waterproof and explosion-proof, replace manual work, but also greatly improve the efficiency of municipal dredging. This design has the following two innovations: 1, the modular design method is introduced into the design, the function module of intelligent dredging equipment is subdivided, and the solution is put forward to provide new ideas for intelligent dredging. 2. Starting from the mechanical structure design of the drainage pipeline dredging equipment, the use of retractable parallel mechanism wall support scheme, so that it has the ability to adapt to changes in pipe diameter size, so as to achieve the design can adapt to different pipe diameter work.