Abstract: In the exploration of karst and mine gob in Ji'nan, Shandong province, restricted by site and human interference, the ground device and well device by ultra-high density resistivity method were respectively adopted to delineate the low resistivity anomaly based on the inversion resistivity results, which guided the corresponding drilling verification work. It is verified by drilling that the low-resistivity anomalies inferred in karst exploration are basically caused by filling karst or crushing zone, while the low-resistivity anomalies inferred in goaf exploration are caused by filling goaf, and the verification results are all good. With various and flexible working forms, large amount of data collection, high working efficiency, less site limitation and high resolution, the method can be used for karst, goaf and other geological hazard investigation.