Nitrogen removal and nitrogen-transformation bacteria in C.alternifolius contructed wetland wastewatertreatment system were studied. The removal rate of TN in the contructed wetland with C.alternifolius were 73.8%;Compared with unplanted constructed wetland system, the removal rate of TN raised 17.4%. The amount of ammonifyingbacteria, nitrobacteria and denitrifying bacteria in C.alternifolius constructed wetland were 7.98×10⁵cfu·g^-1(sand), 1.95×10⁵MPN·g^-1 (sand) and 5.89×10⁴ MPN·g^-1 (sand), respectively; In contrast to unplanting system, the amount of ammonifyingbacteria had no obvious difference,but the amount of nitrobacteria and denitrifying bacteria were 1 order of magnitude higherthan those in the unplanted system.