The thickness of permafrost is an important hydrocarbon accumulation factor for gas hydrate in permafrost areas. There are various exploration methods with different characteristics. In this paper, with the higher cost audio magnetotelluric (AMT) as the detection technology and the Muli area of Qinghai as the study area, AMT forward modeling of numbers of typical models was carried out, then one-dimensional adaptive regularized inversion and analysis were conducted. The results show that the logarithmic derivative curve of one-dimensional regularized inversion (or called the delamination factor curve of stratigraphic interfaces) can be used to divide well the bottom boundary of permafrost. Good results of exploration permafrost thickness application in Muli area were achieved. This means can play an important role in target prediction of gas hydrate in permafrost areas. The study of two cross-sections through the Well DK9 shows that the permafrost thickness near Well DK9 changes little and the permafrost thickness is from 60 meters to 100 m, and these facts provide good conditions for the cap of the gas hydrate concentration. Detection results near Well DK9 are as follows.The permafrost thicknesses of section DK9-2 that is perpendicular to the direction of faults is from 60 meters to 100 m. The permafrost thicknesses of section DK9-1 that is parallel to the direction of faults is from 68 meters to 92 m.