By analysis of climatology foundation data for implementing rainwater-harvesting efficiently agriculture, and the combinative current work foundation the rainwater-harvesting engineering techniques, such as managing surface of the catchment, constructing cellar of rainwater harvesting and facilities of water supplying, were discussed. The experiment of rainwater harvesting for improving water use efficiency was conducted. The limited compensation effect and saving water technique based on agronomic theory were studied on film-mulching rape, greenhouse vegetable, and potato. The results showed supplemental irrigation in key stage of crop requiring water could fulfill water supplying compensation or super-compensation effect and increase water use efficiency and the dry area agriculture could keep on the stability development.