A field experiment was conducted during the 2023-2024 growing season on the Weibei rainfed highland to investigate the effects of summer green manure sorghum-sudangrass biomass incorporation on grain yield and water use efficiency of subsequent winter wheat. A summer fallow treatment was used as the control(CK), and three incorporation treatments were established: whole biomass incorporation without mowing(M₀), incorporation of one-third mowed biomass(M₁), and incorporation of half mowed biomass(M₂). The effects of different biomass incorporation methods on soil water storage, leaf photosynthetic characteristics, aboveground biomass accumulation, grain yield, and water use efficiency of winter wheat were evaluated. The results showed that sorghum-sudangrass cultivation significantly decreased soil water storage in the 0-200 cm soil profile before winter wheat sowing, with reductions of 1.31%-1.93% compared with CK. Sorghum-sudangrass biomass incorporation significantly increased leaf net photosynthetic rate of winter wheat at anthesis and grain-filling stages, with increases of 17.34%-46.97% and 6.27%-25.33%, respectively. The leaf water use efficiency under M₁ was significantly improved by 12.72%-18.79% from jointing stage to filling stage. Biomass incorporation promoted aboveground biomass accumulation of winter wheat, with mature-stage aboveground biomass increasing by 18.47%-38.88%. The increase in grain yield was mainly attributed to enhanced spike number(7.77%-15.94%) and thousand-grain weight(2.50%-4.48%), resulting in a 6.37%-13.97% increase in grain yield and an 8.85%-23.60% improvement in yield water use efficiency. After one rotation cycle, soil water storage under M₀ and M₂ was significantly reduced by 2.22% and 2.92%, respectively, compared with CK, whereas no significant difference was observed under M₁. The M₀ and M₁ treatments significantly reduced seasonal water consumption of winter wheat, with the greatest reduction observed under M₁(6.53%). All sorghum-sudangrass incorporation treatments significantly increased winter wheat water use efficiency, and M₁ showed the greatest improvement(23.60%). Overall, summer cultivation and biomass incorporation of sorghum-sudangrass during the fallow period improved photosynthetic performance, enhanced water use efficiency, and increased grain yield of subsequent winter wheat under rainfed conditions on the Weibei highland. Among the tested incorporation methods, incorporation of one-third mowed sorghum-sudangrass biomass exhibited the most favorable agronomic performance.