Abstract: Parallel underground pipeline is a difficult point in urban underground pipeline detection. Because of the close distance between the two pipelines, electromagnetic fields are superimposed on each other. The use of pipeline meter can not accurately detect the position of the pipeline. Through the analysis of the 70% fixed-depth method of the pipeline instrument, the relationship between the position of the underground pipeline and the observed horizontal magnetic field is simulated by computer, and the joint inversion of the pipeline line instrument and the geological radar detection data is carried out through the computer program module to obtain the visual data and significantly improve the parallel pipeline detection accuracy.