Abstract: The oilfield A is located in the Weixinan Depression of the Beibu Gulf. The 2nd member of the Neogene Jiaowei Formation is the main reservoir. It consists of various sedimentary microfacies which vary in thickness and depositional characteristics. Such differences restrict the description of sedimentary microfacies for inter-well reservoir. In this paper, we recognize the types of sedimentary facies according to the analysis data from drilling wells. The oilfield A is an offshore oilfield in its early stage of development. There are few drilling wells scattered in the region. The only choice is to fully use the high resolution 3D seismic data to carry out the study of seismic sedimentology. The minimum isochronous research units, such as the J2I-1 and J2I-2, are determined using the frequency division interpretation technique and stratigraphic slice technique. They are regarded as the seismic attributes time window. Correlation of the seismic attributes and thickness of the sand bodies is carried out. And the seismic attributes, which have maximal correlation coefficients with the thickness of sand bodies, and the seismic section features are used to define the plane distribution pattern of the sedimentary facies. Upon the spatial distribution pattern of sedimentary microfacies of J2I-2 and J2I-1, the evolution of sedimentary facies from nearshore sand bars to shallow water is established.