Objective This study aims to determine the optimal irrigation timing under the single-irrigation mode during the growth period for winter wheat in Hebei Province. Methods Using winter wheat cultivar Jimai 22 as the test material， a field experiment was conducted over two growing seasons （2021-2022 and 2022-2023）. Three irrigation and nitrogen topdressing timing treatments were implemented： at the 4th （T4）， 5th （T5）， and 6th （T6） leaf visible stages in spring. The effects of irrigation and nitrogen topdressing at different timings on wheat water consumption characteristics， dry matter accumulation， grain yield， and its components were analyzed. Results Under the condition of single-irrigation mode during the growth period， the proportion of water consumption sources and the stage-specific distribution of water consumption in wheat were significantly influenced by the climatic year type. Delaying irrigation had no significant effect on soil water storage consumption or total water consumption throughout the entire growth period and during each stage before and after anthesis， and only promoted the utilization of deep soil water in the 2022-2023 growing season with more precipitation. Pre-sowing soil water storage and water use efficiency showed significant positive correlations with grain yield， while total water consumption showed no significant correlation. Therefore， ensuring water supply at critical stages was more important. Spike number was significantly positively correlated with yield， and grain weight per spike was significantly negatively correlated with yield. Delaying irrigation decreased spike number but increased grain weight per spike. The T6 treatment yielded the lowest during both growing seasons， and the fundamental reason for the yield reduction was that the decrease in spike number exceeded the increase in grain weight per spike. In the 2021—2022 growing season with a pre-sowing soil water storage of 655.74 mm， the T5 treatment showed a slight decrease in spike number and achieved the highest yield. In the 2022-2023 growing season with a pre-sowing soil water storage of only 541.24 mm， the T5 treatment showed a larger decrease in spike number， and the T4 treatment achieved the highest yield. Conclusion Under the single-irrigation mode during the growth period for wheat， prioritizing a higher spike number is key to achieving high yield. When pre-sowing soil water storage is greater than 600 mm or spring rainfall is sufficient， the irrigation can be postponed to the 5th leaf visible stage in spring to balance the grain weight. When pre-sowing soil water storage is less than 550 mm or in drought years， the irrigation must be conducted at the 4th leaf visible stage in spring to ensure spike number. The research findings can provide a theoretical basis and technical support for the water-limited and high-yield cultivation of winter wheat in Hebei Province.