The dissolved oxygen distribution and nitrogen removal effect in different structures of wetlands were investigated by two groups of comparison experiments (vertical flow with horizontal flow; singlestage with threestage horizontal flow). It was found that the different hydraulic flow patterns in different structures of wetlands would result in different oxygen distribution and nitrogen removal effect. The special structure design and hydraulic flow pattern of vertical flow wetland were favorable to its dissolved oxygen distribution

which could increase 0.17 mg/L in local area than that in horizontal flow wetland. The nitrogen removal effect of vertical flow wetland was better than that of horizontal flow wetland in the same operation conditions. The removal efficiency of NH+4-N and TN could increase 9% and 5% respectively in vertical flow wetland than that in horizontal flow wetland. Because of reaeration in contacting channels of threestage wetland

the removal efficiency of NH+4-N and TN reached 66% and 71% respectively

which improved 8% and 5% respectively than that of singlestage wetland. In addition

threestage wetland could keep higher nitrogen removal effect even in low operation water level

and the range of its best hydraulic retention time(HRT) was extended.