With combination of a Position Sensitive Device(PSD) and other components,a kind of detecting system in interpostion was developed for detecting underground pipeline.The system detected the orientaion data at different measuring sites to obtain the orientations of underground pipeline by walking along the pipeline,which could be used in those pipeline with inter diameter of 80～130 mm and bend diameter of 50～1 000 m ignoring the burying depth,the concentration of pipeline and other environments.The analyzing results of experiment show the relative error of the detecting method is 7.45% in horizontal orientation and 1.07% in vertical orientation.