A field experiment was conducted to determine the regulation of crop photosynthesis and output and water saving effect under ridge and furrow rain harvesting with supplemental irrigation in Guanzhong irrigation district. The experiment was set with 5 treatments with irrigation at returning green stage, and the widths of both ridge and furrow being 60 cm. T₁, T₂ and T₃ were in the ridge and furrow rain harvesting planting pattern, with the irrigation volumes being 0, 375 and 750 m³·hm^-2 respectively, T₄ was flat planting with irrigation (border irrigation) of 750 m³·hm^-2 and CK was flat planting without irrigation. Effects on winter wheat photosynthetic organs, photosynthetic rate, yield and water use efficiency, etc. were tested. The results showed that compared with T₄, T₁, T₂ and T₃ treatments  increased the grain yield by 2.8%, 9.6% and 18.9%, improved the harvest index by 2.0% to 8.5%, advanced the flag leaf chlorophyll content by 41.9% to 64.4% significantly, and improved the 0-40 cm layer soil moisture content by 0.1%-4.6% during the whole growth period. Photosynthetic rates at the flowering and filling stages also increased by 22.3% to 54.2% and -4.3% to 67.2%, respectively. Total  water use efficiencies (WUE_y) were 17.9%, 10.4% and 15.4% higher than that of T₄, and 69.3%, 58.6% and 65.7% higher than that of CK (P<0.05), respectively, and enhanced precipitation utilization efficiency (PUE) by 94.3%-124.5% than CK. Leaf areas of T₂ and T₃ treatments at each growth stage were significantly higher than that of T₄ and CK, irrigation water use efficiencies (IUE) were 119.1% and 18.8% higher than that of T₄, respectively. Therefore, it was concluded that ridge and furrow rain harvesting cultivation could maintain higher grain yield than border irrigation without irrigation or with irrigation reduction by 50%. The utilization efficiency of irrigation water under the condition of irrigation reduction by 50% was improved significantly, and the ridge and furrow rain harvesting could significantly improve whole cropland water use efficiency in the year of less rainfall.