Abstract: Shanghai Petroleum-Chemical Industry Combine lies in the middle of the northern coast in Hangzhou Bay. In order to compare the ecological changes in the Bay before and after the operation of the Combine,a survey has been conducted since May,1975 for the benthic faunal community in the soft bottom intertidal zone along the northern coast in the Bay. In all, five sampling sections were chosen, namely sections A, B, C, D and E respectively. This paper, for the first time, reports the annual data of benthic fauna taken for the periods from May 1975 to July 1976. The results indicated that the number of species in this survey area were comparatively poor.For five sections,only 82 species of macrofauna have been identified,in which, 23 species were found to be dominant species. Species composition was dominanted by Crustaceans.Both the habitat density and biomass were also comparatively low, the mean were 442 Indiv./m² and 22.1 gram./m² respectively. Except for section A, number of species, density and biomass in all other sections turned out to decline progressively from high tide regions to low tide regions. The calculation of "percentage community affinity" for five sections indicated that sections B, C, D and E were very similar. The similarity of community at sections B, C, D and E were equally different from that of section A. The seasonal variation of organisms in this area could be attributed to the seasonal fluctuations of temperature and the seasonal transport of sediments due to seasonal winds. The community structure in this area was normal. The results from the analysis of the contents of adverse matters in water and substrate showed no sins of pollutions in this area.