Abstract: While numerous studies on abscisic acid (ABA)-enhanced drought tolerance in crops have been conducted under pot experiments, research regarding the regulation of growth and development, yield improvement effects, and underlying mechanisms through field spraying of ABA in field-grown cereal crops remains poorly documented. This study addressed recurrent drought stress during winter wheat growing seasons in the North China Plain. Using cultivar Keyi 6259, two irrigation regimes (normal irrigation W1 and deficit irrigation W2) were established. Under two water gradients, ABA formulations were applied via foliar spraying: a single-component preparation (S-ABA, A1) and a compound formulation combined with indolebutyric acid (IBA-ABA, A2), using water spray as the control (A0). Leaf gas exchange parameters during the flowering and grain-filling stages of winter wheat were measured using a LI-6800 portable photosynthesis system (Li-cor Inc., USA). Concurrent determinations included leaf water potential, leaf ABA content, osmotic adjustment substances (e.g., soluble sugars, free proline) in leaves and (e.g., soluble starch synthase activity) grains, and malondialdehyde content as an oxidative stress marker. Differences in winter wheat yield, photosynthetic characteristics, and osmoregulation parameters across treatments were analyzed to explore the alleviation effects of distinct ABA formulations on field crop drought stress and their regulatory mechanisms in photosynthetic physiology. The results demonstrated that: 1) Under deficit irrigation (W2), spike number and 1000-grain weight were significantly lower than under normal irrigation (W1). Both A1 and A2 treatments markedly increased grain yield, grains per spike, and grain soluble starch synthase activity relative to the control (A0), with A2 specifically enhancing 1000-grain weight. Compared to the control group (W1A0), the W1A2 and W2A2 treatments achieved significant yield improvements of 19.6% and 13.0%, respectively. 2) Compared to W1, the W2 treatment significantly inhibited the net photosynthetic rate of winter wheat leaves, with an average diurnal reduction of 14.8%. The enhancement effects of A1 and A2 treatments on the net photosynthetic rate varied depending on irrigation regimes and diurnal phases. Relative to W1A0, W1A1 increased the net photosynthetic rate by 23.5% during the noon period (11:30), while W1A2 increased the net photosynthetic rate by 19.6% (08:30) and 19.1% (15:30), respectively. Under deficit irrigation (W2A0), only W2A2 showed significant net photosynthetic rate improvements: 20.0% at noon (11:30) and 16.4% in the afternoon (15:30). 3) Under W2, the diurnal accumulation of leaf ABA content across measurement periods exhibited varying magnitudes of increase compared to W1. Specifically, at 11:30 and 15:30, W2 treatments showed ABA increases of 15.9% and 12.3%, respectively. However, leaf water potential under W2 was significantly reduced by 10.9% only at 08:30 relative to W1. Furthermore, all spraying treatments (A1 and A2) elevated leaf ABA content and decreased leaf water potential compared to W1A0. These coordinated responses of ABA and leaf water potential contributed to the regulation of stomatal conductance, thereby enhancing intrinsic water use efficiency. 4) Exogenous ABA application not only suppressed the accumulation of malondialdehyde under drought stress, but also increased the contents of soluble sugars and free proline. This significantly enhanced the osmotic adjustment capacity of winter wheat and mitigated drought-induced damage. These findings provide robust agronomic references for optimizing plant growth regulator applications in practical farming, while also offering essential datasets to facilitate scaling-up approaches in crop yield prediction models across spatial domains. To sum up, this study confirms that field foliar ABA spray improves stomatal regulation, osmotic adjustment, and drought tolerance in winter wheat under deficit irrigation, thereby increasing water use efficiency and grain yield, providing scientific support for ABA-formulation application in field grain crops.