[Objective] The paper aims to further reduce pollutant concentration and improve the reclamation rate of wastewater in iron and steel enterprises. [Methods] We adopted two sets of horizontal subsurface flow constructed wetlands for the treatment of discharged coking wastewater in iron and steel enterprises, and investigated the impacts of wetland vegetation with and without organic mulches on the treatment of discharged coking wastewater by constructed wetland in winter through the monitoring and analyzing the turbidity, chemical oxygen demand(COD), total nitrogen(TN), and total phosphorus(TP) concentrations in influent and effluent. [Results] In low-temperature season, the hydraulic retention time was 5 days, the average removal rates of turbidity, COD, TN, and TP was 68.55%,14.94%,14.20% and 71.26% in constructed wetland without organic mulches while the average removal rates of those in constructed wetland with organic mulches was 72.54%, 21.62%, 20.50% and 71.88%, respectively. The removal rates of COD and TN increased by 44.68% and 44.45%, respectively. [Conclusion] Organic mulches could be used as insulating material to help increase the purification rate of constructed wetland under the low-temperature condition.