Brachionus calyciflorus Pallas were cultured in both single and group rotifers in the medium of 1.0, 0.5 and 0.25 mL under the experimental conditions of 25℃, light intensity about 4000 Ix(LD=18:6) and the food concentration about 1.0×10⁶ cells/mL of Chlorella sp.In single culture, the mean egg numbers per mother female were 12.0 ind., 13.8 ind.and 7.8 ind.The percentages of mictic female of offsprings were 46.38, 53.49, and 55.83 respectively.In group culture the mean egg numbers were 8.7,3.1 and 2.65 inds.,respectively.And the percentages of mictic females of offsprings were 41.70, 53.59 and 54.26 respectively.There were significant differences between the percentage of mictic females of offsprings and the densities of mother females (F=3.45,α0.05). Put one rotifer in every dish. one of the dishes was precooled to 5℃ as sudden cold shock (SS) treatment, and was kept for 2 hrs at 5±TC, another dish was cooled gradually from 25℃ to 5±1℃ during one hour,then was kept at 5±1℃ for one hour again,as the gradual cold shock (GS).After the treatment, both dishes were moved to 25℃, and cultured at 25±1℃ over the experiments, the third dish was left at 25℃ as contrast (C).The mean egg numbers produced by mother females were 10.8, 9.2 and 12.6 ind, respectively.The per-centages of mictic female of offsprings were 32.9, 20.7 and 16.87, respectively.The results show that the difference between SS and C is significant (t=2.16,α=0.05), but both differences between GS and SS, GS and C were not significant (t=l.32 and 0.52, α=0.05).