An external aeration and intermittent circulation were used to improve the nitrogen removal performance of subsurface flow constructed wetland (SSF CW) in landscape garden ponds. Nitrification was the main mechanism of ammonium-nitrogen (NH4+-N) removal and partial nitrification/anaerobic ammonia oxidation was a minor process. Field measurements yielded a removal rate of NH4+-N of 0.266-0.566 gN/d m(2) and a corresponding temperature dependent rate constant of 0.184 d(-1) to 0.377 d(-1) representing an improvement over nitrogen removal. The nitrate-nitrogen (NO3--N) removal was degraded to the background level of NO3--N concentration in an environment with a high concentration of dissolved oxygen. The NO3--N removal rate ranged from 0.0393 gN/d m(2) to 0.0825 gN/d m(2) and resulted from aerobic denitrification, indicating that external aeration and intermittent circulation effectively improved oxygen transportation in SSF CW. This could remove NO3--N of the effluent of SSF CW when using in-tank aeration to improve the nitrogen removal performance of SSF CW. (C) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.