Abstract: 【Objective】 To elucidate the mechanism of action of plant growth regulators under drought stress on winter wheat and address the issues of uneven distribution of water resources and low water use efficiency in agricultural production. 【Methods】 A split-plot experiment design was adopted, with two water treatments: seedling stage drought stress (25% of normal irrigation amount, denoted as I₁) and jointing stage drought stress (25% of normal irrigation amount, denoted as I₂). Three concentrations of chlormequat (1.67, 2.22, 3.33 g/L) were set up (denoted as C₁, C₂, C₃), with water (CK) as the control. The effects of foliar application of chlormequat on the photosynthetic characteristics, dry matter accumulation and transport, and yield of winter wheat under different irrigation drought stresses were analyzed. 【Results】 Under both irrigation treatments, jointing stage drought stress significantly reduced the flag leaf area and individual plant leaf area by 87.73% and 65.40%, respectively. After anthesis, the Pn value and Tr value of winter wheat flag leaves decreased, Ci concentration increased, reproductive growth time was shortened, and the accumulation and transfer of photosynthate decreased. This led to a decrease in the number of spikes, grains per spike, and thousand-grain weight, ultimately resulting in a yield reduction of 40.28%. Foliar application of chlormequat mitigated the negative impact of drought stress on winter wheat yield reduction. Under C₂ and C₃ concentrations, the flag leaf area and individual plant leaf area of winter wheat increased; chlormequat solution enhanced the photosynthesis of winter wheat and delayed plant senescence. Under both treatments, the peak photosynthetic rate after anthesis was higher than CK by 28.62%, 36.23%, 34.19%, and 21.62%, 21.27%, 45.87% for C₁, C₂, C₃ concentrations, respectively. The decline in photosynthetic rate from peak to end of the growing period was reduced; under chlormequat treatment, the dry weight of mature vegetative organs, dry matter translocation amount, and translocation rate all increased, with the highest values reached under C₂ concentration. Under both irrigation treatments, the yields of wheat treated with C₁, C₂, C₃ concentrations of chlormequat increased by 0.32%, 16.08%, 11.75%, and 4.52%, 23.60%, 6.42%, respectively, compared to CK. 【Conclusion】 Combining irrigation treatment and chlormequat concentration, drought stress reduces the number of spikes, grains per spike, and thousand-grain weight, thus leading to a decline in yield. Pre-flowering drought stress has a greater impact on yield, especially during the jointing stage. Exogenous application of chlormequat can improve the adverse effects of drought stress on wheat to varying degrees, with the best results observed at a concentration of 2.22 g/L.