A series of experiments were carried out to investigate the hydraulic characteristics of integrated verticalflow constructed wetlands (IVCWs) and its effects on their purifying efficiencies. The results of the experiments in Small Scale Plots (SSPs) and Medium Scale Plot (MSP) of the constructed wetlands showed the plant root and rhizome are the main factors affecting the hydraulics and the purifying efficiency. The hydraulic characteristics of a constructed wetland include influent load, effluent quantity and velocity, retention time, porosity volume of the wetland, etc. They are related to almost every flow characteristics and patterns of the in_fluent. Purifying efficiency increased with flow rate and effluent quantity of the plots. For plots with plants in both chambers, these two chambers were connected in the bottom through which the water exchanged. The plots with a longer retention time showed a better purifying efficiency than the plots with a shorter one. Unplanted plot showed a relatively longer retention time and a lower purifying efficiency. The measured retention times were much longer than the theoretic values, especially in SSPs, which may mainly be due to the biological absorption and physical adsorption of the tracer by plant roots, microorganism and substrates. The plots with a slower washout velocity and rate of the tracer showed a higher purifying efficiency. As the SSPs and MSP exhibited a similar pattern, the washout rate was believed to be mainly affected by the substrate while the plant root and microorganism had a relatively minor influence on it. The influent load affected the other hydraulic characteristics and showed rather a complicated variation. Based on the result of experiments in MSP, the higher intluent load had a slower effluent velocity and smaller effluent quantity, as well as a lower purifying efficiency. However, ifthe influent load is too small, the purifying potential would not be fully developed. Therefore, there must have an appropriate influent load for a certain wetland. The hydraulic characteristics are thought to have a great affects on the purifying efficiency by influencing the plant growth and activity of microorganism in wetland.