The influence of silver carp (Hypopkthalmichthys molitrix) and bighead (Aristickthys nobilis) on the zooplankton community structure in Dcnghu Lake f Wuhan was studied using enclosure method during April-July 1990.In the enclosures where silver carp and bighead were stocked,the average densities of the Protozoa and some small-sized rotifers were high,while those of crustacean and large-sized rotifers were low.In the enclosures without fish,the results were opposite.The average biomass of zooplankton was much higher in the two enclosures without fish (55.035 rag/L and 38.374mg/L) than in the two enclosures with fish (3.028mg/L and 3.490mg/L) during April-July 1990.The examination of the size-frequency distributions of the crustacean (copepod nauplivis excluded) shows that the frequency of the large-sized crustacean was higher in the enclosures without fish than in the enclosures with fish.The enclosure experimental results show that the feeding of silver carp and bighead resulted in the dominance of small-sized zooplankton instead of large-sized ones.