The granite type uranium deposit mainly occurs in the interior or at the edge of a rock body. The investigation of the developmental conditions of a rock body thus has significance for uranium deposit exploration. The controlled source audio frequency magnetotelluric (CSAMT) method and its applications in Weijing area were described in this paper. Based on geological data and rock resistivity as well as CSAMT data, the authors found the thickness of the granite rock mass and the deep development of the contact zone between the granite and the metamorphic rock, and the good results were verified by drilling. A comprehensive analysis shows that CSAMT method has fairly good resolving power in vertical direction. According to results of CSAMT method, the authors detected the thickness of rock bodies as well as the position and the deep characteristics of structures. In addition, the distribution characteristics of the zones of fractures, fissures and vein bodies were detected too. The CSAMT method is an effective means for uranium deposit exploration.