The production potential of ridge-furrow plastic film mulching (RFPM) cultivation is often constrained by insufficient water-nitrogen synergy. Regulated deficit irrigation (RDI) combined with controlled-release urea (CRU) blended with normal urea (NU) may optimize this synergy. However, whether this approach can enhance water-nitrogen coupling and improve winter wheat yield stability under RFPM remains unclear. A four-year field experiment (2021-2025) was conducted under RFPM with three RDI levels (W1: 30% ETc, W2: 55% ETc, W3: 80% ETc) and four CRU:NU ratios (N1: 0:100, N2: 100:0, N3: 30:70, N4: 70:30). Compared with N1, the N2, N3 and N4 treatments increased soil water storage by 2.49-9.72% at jointing but decreased it by 2.75-13.47% at anthesis and maturity (p < 0.05), indicating improved spatiotemporal matching of water and nitrogen supply. Specifically, the N4 treatment maintained lower nitrate-N content in the 0-100 cm soil layer at jointing (reducing leaching risk) while increasing it at anthesis to match post-anthesis crop demand. Under W2, the N4 blend significantly enhanced aboveground growth, regulated endogenous hormone balances (increasing ABA, IAA and Z + ZR contents while decreasing GA content in both superior and inferior grains), prolonged the active grain-filling period by 1.3-2.5 d, and increased the mean filling rate by 12-18% compared with N1. Consequently, N4 achieved the highest grain yield, which was 21.8-42.6% higher than that under N1 at the same RDI level (p < 0.05). The temporal stability and sustainable yield index of W2N4 were also the highest among all treatments. Moreover, compared with N1, N4 significantly improved WUE and NPFP at all three RDI levels, with average increases of 26.36% and 30.00%. Thus, the combination of 55% ETc irrigation with W2N4 is recommended as an effective strategy to enhance water-nitrogen coupling, improve yield stability, and increase resource use efficiency in RFPM systems in arid and semi-arid regions.