Abstract: The technique of petroleum exploration based on microbiology is illustrated in this paper,which is applied to actual petroleum geochemical exploration in the known and unknown areas in Xihu sag,east China Sen.The anomaly of hydrocarbon-digesting bacteria in sediments can effectively indicate and predict the potential information underground.The results from the oil/gas prediction by microbiology are consistent with geological,geophysical,and drilling data available,which suggests a promising application.