Abstract: Based on the grainsize analysis results of 108 surface samples taken from the intertidal zone of Tianjin area, the authors divided the types of the sediment, and discussed the distributed characters of granularity and the sedimentary process of the intertidal zone. Three lithology zones were got on the intertidal zone of Tianjin area with the boundary of Haihe River and Duliujianhe river mouths. From the north of Haihe river mouth to the Jianhe river mouth is clayey-silt area. Sandy-silt area with mixed lithology distributes between the south of Haihe river mouth and the Duliujianhe river mouth. From the Duliujianhe river mouth to the Qikou is also the clayey-silt intertidal zone. The sedimentary dynamics of the intertidal zone is different. The intertidal zone on the north of Haihe river mouth is a tidal dominate environment, but on the south is a river dominate environment with tide transformation. The water energy on the intertidal zone from Lvjuhe to Duliujianhe river mouth was strong in the early periods, but was also influenced by tide transformation later. The intertidal zone on Qikou area is a tidal dominate environment.