Abstract: In the regular inspection of urban gas buried polyethylene pipelines, it was found that the entanglement of plant roots led to small and dense black silk marks on the surface of pipes. It was difficult to judge the damage of plant root exudates to the pipe bodies from the appearance. After sampling the problem pipes, the wall thicknesses were measured, the parts with trace were examined by penetrant testing, and the internal and external surfaces of the pipes were tested with infrared spectrum. The results show that although plant root exudates affected the color of the pipe bodies, but they did not change the thicknesses, density and composition of the pipes, so they had little effect on the safety of the pipes. However, in subsequent inspections, attention should also be paid to the problem of pipe tensile deformation caused by root entanglement.