Abstract: The sedimentary facies of the lower IV interval of the Shahejie Formation in Paleogene in Bonan sag are studied through comprehensive analysis of drilling and logging data Five facies are identified including fan- delta, braided river delta, near- shore submarine fan, lake and salt -lake. Fan - delta facies exists in the south of the study area; near- shore submarine fan facies exist at the northern margin; braided river delta facies in the east and west; while lake and salt - lake facies developed in the central part. These studies provide a theoretical basis for development geological study of reservoirs in this interval.