The changes of exposure to pollutants,simplified geomorphic structure,and altered hydrographs of streams combine collectively known as the"urban stream syndrome",The symptoms include elevated concentrations of nutrients and contaminants,altered channel morphology and stability,and reduced biotic richness and diversity,with increased dominance of tolerant species.There is rarely single conventional restoration measures could solve the problems above altogether,Therefore,based on two-stage stream and subsurface constructed wetland,an in-stream gravel bed system was developed.This kind of design,including the water quality improvement,habitat restoration and landscape improvement has tackled the problem of large land requirement of constructed wetland which is usually applied for stream water purification.