Abstract: The population density, rate of egg to female and percentage of micticfemale produced by rotifer Brachionus calyciflorus Pallas cultured in variousconcentrations of rare earth-elements (REE) were studied at 15±1℃, 25±1℃ and30 ±1℃, respechvely. The density increased with increase of the concentration ofREE at 15℃. The optimum concentration was 0.005 mgL-1, the rotifer populationdensity was 92.4 ind.mL-1 and higher in mis concentration than in others. At 25℃,the rotifer densities increased quickly at concentration of 0.001mgL-1, and was higherand the Percentage of mictic female was lower than in others. Although the rotiferpopulation density increased quickly in short-term at concentration of 0.005mgL-1 at30℃, the duration of highest density was cut down. The rotifer population densitydecreased at the concentrahon of 0.010mgL-1.