The effects of such geochemical methods as soil survey, rock survey and stream sediment survey in large-area geothermal prospecting are dealt with and compared in this paper. It is demonstrated that geochemical soil survey and stream sediment survey yield the best results, while geuchemical rock survey also gives pretty good effect. The indicator elements consist of Hg, As, Sb. A dis cussion is made on the potentiality of the Rehai geothermal field in the light of exploration geochemistry, indicating that as this geothermal field is charac terized by large size, high temperature and considerable reserves, there exists bright prospect for its exploitation and utilization.