Abstract: 6 heterotrophic nitrobacteria are screened from bio-ceramic reactors.And sodium acetate and am- monium chloride are used as carbon and nitrogen source to foster bacteria for the characteristic study of nitrifi- cation.COD removal rate could reach over 45%,TN and NH₄-N removal rate could reach over 60 %,and al- so it has the nitrification function of producing NO_x-N.By the method of PCR-DGGE,this paper studies the dynamic changes of the SBR reactor.The PCR-DGGE profiles show that shift of microbial diversity corre- sponds to the effect of nitrate removal.1 d and the 15 d similarity is 75%,which microbial diversity is the highest.1 d and the 30 d similarity is the lowest which is just 52.9496,15 d and the 30 d.similarity is 70.59%.wgyl,wgy3 and wgx5 are dominated bacteria in sequencing batch reactor.