General characteristics of the economically important invertebrates were studied through monthly surveys with twin trawl in the period from September 1985 to August 1986. Sampling was made at each of the 33 stations. A total of about 145,000 individuals of invertebrates, belonging to 67 species, were collected and identified during the surveys. Among them, 48 species were crustaceans and 15 species were molluscs. Besides, data of fishing statistics and environmental factors were collected and analysede.The abundance and biomass of main invertebrate species in the investigated area changed seasonally. The abundance and biomass were 13, 318ind /k㎡ and 313.3kg/k㎡in summer, 12, 894 ind/k㎡and 523.4kg/k㎡ in autumn respectively,which aer much higher than 2283 ind/k㎡ in winter. The ecological characteristics and seasonal numerical distribution of some dominant species. such as the brackish water species Exopalaemon annandalei,E. cariinicauda;the catadromous freshwater species Eriocheir sinensis and the common marine species: Portunus trituberculatus, Ovalipes punctatus, Solenocera crassicornis, Trachypennaeus curvirostris, Parapenaeopsis hardwickii, P. ctlurirostris and Sepiella maindroni, were briefly dcscribcd. The main purpose of the study was to predict the impact of the Three Gorges Project the invertebrate resources. On the basis of fully understanding of the early life history of the woolly-handed crab, Eriocheir sinensis, which is one of the most important economic invertebrate in Changjiang Estuary, a conceptional model was developed. Furthermore, by stepwise regression analysis of multi-variable the relationship between the abundance of the crab seed (Megalopa )and various environmental factors, such as the monthly runoff flow of the Changjiang River and the precipitation, etc. was analysed. According to the presumable regulation of the rived runoff by the Three Gorges Project, the impact on the yield of the seed of wollyhanded crab was estimated. Similarly, the catch yields of the white shrimps and crabs were assessed. Some possible effects of the project on the resources, such as the changes of the distribution patterns of some invertebrate animals and the increase or decrease of their yield, are predictable.