The invention discloses a rainwater collection and water-saving irrigation system used for an upland sloping field. The system comprises a rainwater collection pond or weir, a high-position water storage reservoir, a plurality of low-position water storage reservoirs, a water pump and a water conveying pipe, wherein the rainwater collection pond or weir is arranged on the middle part or lower part of a valley; the high-position water storage reservoir is arranged on the upper part of a hill body with maximum height in each hill body close to the rainwater collection pond or weir; the plurality of low-position water storage reservoirs are arranged on each hill body at the periphery of the high-position water storage reservoir respectively and are lower than the high-position water storage reservoir; the water pump is arranged beside the rainwater collection pond or weir; a water inlet of the water pump is connected with the rainwater collection pond or weir, and a water outlet of the water pump is connected with the high-position water storage reservoir; and the water conveying pipe is laid between the high-position water storage reservoir and each low-position water storage reservoir. By using the rainwater collection and water-saving irrigation system, surface runoff water produced by rainwater is accumulated in the rainwater collection pond or weir, water in the rainwater collection pond or weir is lifted to the high-position water storage reservoir by the water pump, water of the high-position water storage reservoir is conveyed to each low-position water storage reservoir through the water conveying pipe respectively, and water accumulated in each low-position water storage reservoir is used for irrigation when the irrigation is needed.