Abstract: A combined structure of rainwater catchment,methane pool, reformed greenhouse was constructed to improve water use efficiency.The results showed that the combination of rainwater catchment,reserving techniques, water saving measures was efficient to resolve the problem of water deficiency in the semi arid region with precipitation of 250～550mm.The combined structure of water catchment engineering,greenhouse, methane pool redistributed light,temperature,water, heat to develop higher benefits economic crops,and improved water use efficiency,which made it possible to develop high yield,and best quality agriculture in this region.Through optimizing the ecological factor in greenhouse,the water use was reduced by 50%～70%,and the soil temperature, night temperature were raised.This combined construction also improved productivity in greenhouse,and efficiently controlled plant diseases, insect pests.Methane pool provided CO₂, part energy source.The shady area back of the greenhouse was exploited by growing shady crops, epiphyte,which contributed to exchange energy, CO₂ between light, shady house.This model could be used as water catchment agricultural development model in the region,and some other new approaches to water catchment agriculture in semi arid region were discussed in this paper.