Abstract: Based on the integrated study results on cores, drilling and geochemical data from FHT structure in Xihu depression, the sedimentary environments of the Lower Member of PH Formation have been identified through large amount of basic researches on sequence stratigraphic, sedimentology and logging geology, although lacking of borehole and other data. It is believed through study that the sand bodies in P8, P9, P10 and P11 layers in the Lower Member of PH Formation are lagoon tidal flat deposits deposited under semi-enclosed embayment environment. In addition, the planar distribution characteristic of sand bodies has been forecasted, and the evolution of sand bodies has been analyzed. In vertical view, from P11 to P8 layers, the sand bodies expanded southeastward, increasing in scale, showing the transgressive sedimentary features in general.