Two laboratory scale constructed wetlands were designed as horizon subsurface flow constructed wetland (HFCW) and vertical flow constructed wetland (VFCW) and were utilized to study the treatment capacity to reduce nitrogen. According to different inflow concentration and height of water surface, HFCW was analyzed in two operational modes and VFCW in four operational modes. The semi-submerged VFCW had the best capacity to remove nitrogen and the total nitrogen removal rate reached to 92% and the removal rate of HFCW was 90%. Moreover, the un-submerged VFCW could reduce 93% ammonia but nitrate removal rate just was 9%. And the removal rates of NH4+-N, NO3--N and TN respectively were 85%, 80% and 81% in submerged VFCW.