The invention relates to the field of geotechnical engineering detection and test, and particularly relates to a method for detecting an underground pipeline with small aperture and great burial depth. The method is characterized in that a strong magnet is placed in an underground pipeline to be detected, an active magnetic source is sent to an area to be detected by adopting a guide rod, then a hole is drilled by the side of the underground pipeline in the area to be detected, a magnetic sensor is placed in the drilled hole so as to measure a magnetic field of the active magnetic source, and accurate location information of the underground pipeline is judged according to acquired magnetic field data. The method has the advantages that the acquisition period is short, the input cost is low, the detection process is high in interference resistance, and the detection result is accurate.