This paper sets forth the prospecting effect of transient electromagnetism to the stratum collapse of mind-out area under highway of Qingdao to Lanzhou. Introducing the field data collected technique of transient electromagnetism, analyzing and studying the resistivity abnormity features of mind-out area and stratum collapse. Finding the distributed location and deepness and taking valuable conclusion. The prospecting effect of transient electromagnetism rests with the choice of array type and other technical parameters. From resistivity and minimum and maximum exploration depth to ascertain minimum and maximum time delay. It is to be very important of holding the potential stratum and grasping the resistivity confine of mind-out area and the surrounding rocks. Specially remarking to distinguish the resistivity difference of mind-out area and cave-ins. Drilling has verified the mind-out area is high resistivity and the cave-ins are low resistivity in this location.