Abstract: This experiment took non-biological floc culture mode as a contrast to study the change rule of water quality factors including ammonia nitrogen and nitrite nitrogen in biological floc Litopenaeus vannamei culture mode.The results showed:biological floc deposition of the test group reached the peak value(15.93±0.31)mL/L at the 35^th day,and then it remained relatively stable,while the biological floc deposition of the control group had been at extremely low level(<1.5 mL/L);there were significant differences between the two groups(P<0.05).Ammonia nitrogen content of the control group reached the peak value(1.05±0.19)mg/L at the 35^th day,while ammonia nitrogen content of the test group increased slowly and was merely(0.37±0.04)mg/L at the 60^th day,which was significantly lower than that of the control group(P<0.05).In this experiment,during the first 15 days,there was no significant difference in nitrite nitrogen content between the test group and the control group(P>0.05).Afterwards,nitrite nitrogen content of the test group increased slowly and tended to be stable,while nitrite nitrogen content of the control group increased linearly and was significantly higher than that of the test group(P<0.05).