According to the monitoring data and information obtained from National Marine Environmental Monitoring Center, the species composition, density, biomass, dominant species andthe trend of biodiversity variation in the ecology-monitoring area of Changli in Hebei Province from 2009 to 2013 were analyzed. The results showed that 5 phylum including arthropods, annelid, mollusks, echinodermata and chordata, totally 17 family and 26 species were identified. The types and number of species were declined annually. The density and biomass were consistent with the characteristics of low tidal zone>medium tidal zone>high tidal zone. The dominant species were changed significantly, by which arthropods, annelid and mollusks appearing alternately. As the decreasing of the number of dominant species, the dominance index went up which suppressed the other species. The Shannon-Wiener’s index(H’), Margalef’s richness index (dMa) were low, and their variation ranges were 0.81~3.23 and 0.48~3.96, respectively. The variation range of Pielou’s evenness index (J) was0.64~0.8, which presented a miniature uptrend and stable status.