Abstract: By utilizing mass spectrographic technique, the author has developed a 36 channel AC analytical apparatus. It has such advantages as rapid, accurate, cheap and practical, and is therefore an effective device in large-scale geoche-mical oil prospecting. This paper gives detailed data on the exploration ef fectiveness and analytical quality of the soil AC method used in geochemical oil-gas prospectig. It also poses some problems which deserve further investi gation.