Application of biochar can be an effective and low cost technique for wastewater treatment while reducing greenhouse gas emissions. In this study, biochar was used as substrates in Vertical flow constructed wetlands (VFCWs) for enhancing the removal of contaminant from low C/N wastewaters with different influent strengths. The removal of organic matter and nitrogen in biochar-added and non-biochar-added VFCWs with different low C/N influent strengths were evaluated systematically. The results demonstrated that combining VFCWs and biochar addition could be an appropriate strategy as compared to conventional VFCWs with average removal of organic pollutants (85%), NH4+-N (39%) and TN (39%) especially at high influent strengths. Meanwhile, N2O emission was also significantly lower in biochar-added VFCWs (138-1008 mu g m(-2) h(-1)) than that in non-biochar-added VFCWs (164-1304 mu g m(-2) h(-1)) under different influent strengths. We believe that VFCWs by adding biochar can be a useful technology for treating low C/N wastewaters.