In order to study the effect of Rhizoma coptidis (R. coptidis) on ammonia nitrogen treatment efficiency of BFT system, 0 g/L, 2 g/L, 4 g/L and 6 g/L R. coptidis were added, which were named as C, T1, T2 and T3, respectively. The ammonia nitrogen and nitrite conversion tests were performed, and the nitrilase and dehydrogenase activities of each group were determined. The removal rate of total ammonia nitrogen in treatment group was higher than that in control group (0.38±0.07 mg/g·h), and the highest was in T2 group (1.49±0.08 mg/g·h). The nitrite removal rate of T1 group (1.38±0.10 mg/g·h) and T2 group (2.05±0.14mg/g·h) was higher than that of C group (0.75±0.06 mg/g·h), and T3 group (0.17±0.05 mg/g·h) was the lowest. After the test, the total suspended solid in treatment group was lower than that in control group (504.00±27.71a mg/L), and the lowest in T3 group (363.33±40.41mg/L). The experimental results showed that R. coptidis could improve the ammonia nitrogen conversion rate of biofloc and reduce the accumulation of total suspended solid.