Abstract: Carbon－to－oxygen ratio spectrometry logging is a oil－bearing layer residual oil logging technique． Its logging results can directly provide residual oil saturation and can identify the logging layers as oil－bearing zones aquifers oil－water contact of water－follded zones． These data can provide basis for field application of measures of water plugging and perforation adding． The characteristics of carbon－to－oxygen ration spectrometry logging technique application results and the problems for attention are introduced taking Wenmingzhai oilfield as an example．