In order to understand the sedimentary characteristics in Sungang area of Biyang Sag, the typical seismic facies and the planar characteristics of seismic facies of the study area were studied by using the seismic facies identification method. Based on the corresponding relation of seismic facies and sedimentary facies, instantaneous frequency planar graph, palaeogeomorphology and the single well facies of some wells, the planar graphs of seismic facies were translated into the planar graphs of sedimentary facies. By the study, four typical seismic facies in the study area were identified, including sphenoid foreset facies, oblique foreset facies, imbricate progradation facies and subparalleling sheet facies. In the northern study area, there are vast braideddelta front subfacies of the different period in the upper sub-member and the lower position of sand groupⅠof He 3 member. In the southern study area, there is only one leafy sand body of fan delta front in the upper sub-member of sand groupⅠof He 3 member, and two leafy sand bodies of fan delta front in the lower position of sand groupⅠof He 3 member.