Constructd wetland system is one of the ecological engineering technologies used on wastewater treatments. In this study, we discussed the treatment efficiencies of oil refining and steel-milling wastewater by four lab-scale constructed wetland systems (0.8-m long by 0.4-m wide by 0.7-m deep), which were all filled with gravel media, and planted with Phragmites communis. The constructed wetland systems were designed into two types: free water surface (FWS) and subsurface flow (SSF) wetland systems, which were discharged with two different types of wastewater (oil refining and steel-milling). The experiments of this study were run by five stages. The experimental results showed that almost all of the contaminants could be reliably removed from wastewater by the constructed wetland systems, especially in the SSF systems. During the experiments, the second stage of the experiments had the best treatment efficiencies, in which the flowrate was controlled at 5mL/min. The hydraulic retention time (HRT) in FWS and in SSF werecalculated equal to 7.5days, and 5.36days, respectively.