Abstract: Six types of seismic facies were classified in Haizhong Sag by the analysis of frequency, continuance, amplitude and geometric shape. The conversion of seismic facies to sedimentary facies was done based on the research of regional geologic setting and sedimentary facies analysis of shallow layers with well drilling. The sedimentary facies of E₂l₃ in Haizhong Sag mainly included river-fluvial plain, shoreshallow lacustrine, braided delta, subaqueous fan and hemi-deep lacustrine which indicated that reservoir strata developed in E₂l₃ in Haizhong Sag. Furthermore, potential source rocks maybe developed in the hemideep lakes developed in the center of the sag and meares distributed widely in the sag.