Three species of crustacean zooplankton i.e. Daphnia carinata, Eucyclops serrulatus, Dolerocypris sinensis,Sand Brachionus calyciflorus were cultured at seven initial densities with Brachionus calyciflorus inoculated at density of 0.35 ind/mL. The controls were made by mono-culturing of these species at corresponding inoculating densities, respectivly. The results showed that the population of B.calyciflorus was suppressed by all of the three species of crustacean zooplankton. The suppression enhanced with initial inoculation densities of them and caused extinction of the B.calyciflorus at the end of some cultures. The population of D.carinata, E. serrulatus, and D. sinensisSchanged differently, however, compared with their respective controls, as they were cultured with the B.calyciflorus. For D. carinata, the population was inhibited by the B. calyciflorus at lower inoculation densities and the inhibition became negligible with increase of the inoculation densities. This suggested a competitive relationship between the D. carinata and the D. carinata, and the D. carinata was superior to the B.calyciflorus in this relations. Different in behavior from that of the D. carinata, both of the E. errulatus and the D. sinensisSwere promoted in population as they were cultured with the B.calyciflorus. The extent of promotion for the D. sinensis was found higher the extent for the E. errulatus. Result of present study denied existence of competitive relation between E.errulatus and B.calyciflorus and between D. sinensis and B.calyciflorus.