Abstract: △C is au important geochemical indicator for prospecting and locating oiland gas amumulations. In view of the fact that no detailed analytical methodwas previously worked out in China,we have carried out a series of experiment.This paper introduces the detailed experimental results of △C analysis,including the optimization of analytical conditions, the interference of carbona-tes other than △C, the precision of the method as well as a description of themeasuring system. The relative standard deviation of thc analytical method lieswithin ±15-25%.