Abstract: Present study on the geothermal system in Wantian geothermal field reveals the relationships between the geothermal characteristics and geological composition. The Wantian geothermal field is associated with particular geological conditions, such as Changde-Anren fault, Chaling-Linwu fault and their derived faults, Wufengxian granite body and the strata of Lower Carboniferous(C₁y¹), with specific geothermal geological background. The effective allocation in time-space of geothermal system consisting of heat source, reservoir and cap rock is a necessary condition for geothermal occurrence. The main geothermal reservoir of the geothermal field is the Lower Carboniferous dolomitic limestone or dolomite, including both of stratified reservoir and zoned reservoir. The Wantian geothermal field is a kind of economical low temperature geothermal resources with medical hot mineral water quality, suitable for mining and with developing prospects.