Abstract: In the drilling interpretation,how to evaluate reservoir property quickly and accurately is a topic which people have been searching continually.In this article,the principle and process of pyrolysis gas chromatography have been introduced,its theoretical basis have been illustrated,fluid sample of different property graph spectra feature in Tuha oilfield reservoir have been summarized,which provided basis for geochemical mud logging technician to identify the fluid property of the reservoir as oil layer,oil and water layer,oil and water content layer,water layer,gas and water content layer,and have gained good applicable effect.