Abstract: A novel and low-cost foam gauging pig was proposed for the issue that the foam pig cannot accurately judge the deformation of the pipeline and remove stubborn residual substances in the pigging process, which may lead to inaccurate results of detection instruments used later or even blockage of the pipeline. Magnetic flux leakage detection principle was used to place magnetic blocks in the polyurethane layer of foam pig, and Hall element was used to measure the change of magnetic field during deformation to obtain the height, form and other characteristics of residual substances for diameter measuring in advance. The design allows the accurate detection of scaling and deformation in the pipeline under complex working conditions to prevent blocking. With the operating foam gauging pig as the research object, ABAQUS software was used to simulate its deformation when encountering residual substances. The results show that when a certain deformation occurs, the larger the density and the thinner the thickness of the foam at the outer layer, or the smaller the density and thicker the foam at the inner layer of the pig, the more accurate the measured displacement variation results will be.