The soil carbonate △C survey now becomes a major method in China's geocbemical petroleum prospecting and has been used in different stages ofsurface geochemical oil-gas prospecting (rough survey, reconnaissance anddetailed investigation, with fairly good results obtained; nevertheless, it hasbeen found that this method fails to yield distinct geochemical anomalies insome areas. In order to raise the effectiveness of △C survey and make it display anomalies satisfactorily in different landscape areas, we performedrather thorough and systematic basic experimental research.This paper describes in detail the result of the study, and points out thecauses of such unsatifactory result in using △C method. It is suggested thatcarbonates with different sorts of thermal phase state be adopted as effectiveindices in different landscape areas to replace the previous method which onlyused a single index (△C) to conduct survey.