The proportion of mine old goaf water in coal mine water disasters is more than 70 %, and most of the water disasters that hurt people are caused by old goaf water. In order to improve the detection effect of coal mine old goaf water, this paper took the old goaf water of No.2 coal mine in Wutongling small coal mine outside Wutongzhuang Mine as the target, and used two detection techniques including the ground-air frequency domain electromagnetic method and the ground intermediate gradient method for comprehensive detection. The detection research showed that through the analysis of the response characteristics of the water abundance model in the old goaf, the intermediate gradient method of the ground-air electromagnetic detection method could theoretically carry out the detection of the old goaf water. The results of the ground-air ' magnetic field method ' and the intermediate gradient ' electric field method ' were compared and comprehensively explained, so as to accurately locate the spatial position of the hydrological anomaly body and achieve the purpose of fine detection of old goaf water. The application of ground-air electromagnetic and intermediate gradient methods to compare the abnormal location and shape could accurately delineate the water accumulation range and spatial distribution of No.2 coal goaf in Wutongling small coal mine. The application effect was good, which provided a new idea for the application of the two methods in the field of mineral hydrogeological exploration.