The population density of rotifer Brachionus calyciflorus increasedwith the culture time increased when 20, 40,80 and 100ng ml-1of vitamin B12were added into medium at 15 e, and the regress equationwas y= e(0.11757+ 0.2974x), y= 416765x1. 2079, y = 717798x1 10175and y= e(016117+ 0.13469x), respectively. The density of rotifer in experimental groupswere significantly higher than that in the control (t= 4.56, 8.15, 8.53 and 9.86 respectively: P1.4366, y= 717461x1. 6533, y= 6.3611x1. 7790and y= 9.064x1. 6872was found in treatment groups andy= 715902x1.50192in the control1The density in treatment groups were higher than that in the control (t value was 16.12,10.17, 5.83 and 5.86: P-1, 40ng ml-1, 80ng ml-1and 100ng ml-1, and was 13.40% in the control.The egg ratios were 1.86, 2.00, 0.73 and 1.81 under this temperature. At 30e, the positive correlation (y =e(0.1376+ 0.4395x), y= e (0.2032+ 0.4856x), y= 3. 4615x1.9522and y = e(0.0220+ 0.48074x)) exist in treatment groups of 20, 40 and100ng ml-1, and the density were higher in treatment groups (t= 3.36, 10.23 and 2.13) than that in the control but forthe group of 20ng ml-1 (t= 0.34). The highest mictic percentages were 18.18, 7.60, 18.18 and 16.67%, respectivelyin treatment groups, and in the control was 66.70%, the maximum egg ratios was 0.70, 1.90, 0.91, 1.09 in treatmentgroup and was 0.95 in the control.