Abstract: As a popular traditional fermented wheat flour product, steamed stuffed buns often suffer from significant quality deterioration of the dough during freezing, frozen storage, and subsequent re-steaming. These quality defects, primarily manifesting as texture hardening, reduced elasticity, surface cracking, and poor sensory acceptance, are largely attributed to the mechanical damage caused by ice crystal growth, the weakening of the gluten network, and the retrogradation of starch. To address these technical challenges, this study aims to systematically investigate the synergistic regulatory mechanisms of soluble soybean polysaccharides (SSPS) and lard (LD) on the quality improvement of frozen and re-steamed steamed stuffed bun dough. Three types of steamed buns with typical fillings—pork (representing a high-fat and high-protein system), cabbage and mushroom (representing a high-moisture and high-fiber system), and red bean paste (representing a high-sugar and high-starch system)—were selected as research models to evaluate the applicability of the additives in complex food matrices. A comprehensive multi-dimensional analytical approach was employed to characterize the physicochemical properties and microstructural evolution of the dough. The textural characteristics were quantified using a Texture Analyzer, while the water mobility and distribution were monitored via Low-Field Nuclear Magnetic Resonance (LF-NMR). Furthermore, the changes in protein secondary structures and starch crystallinity were elucidated using Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD), respectively. The microscopic morphology of the dough was visualized using Scanning Electron Microscopy (SEM). The results demonstrated that the combined addition of SSPS and LD significantly improved the eating quality of the re-steamed steamed stuffed bun dough compared to the control group and single-addition groups. Texture profile analysis indicated a significant reduction in hardness and chewiness, alongside a marked enhancement in elasticity and resilience (p<0.05). LF-NMR analysis revealed that the additives significantly altered the state of water within the dough matrix. Specifically, the bound water content in pork, cabbage and mushroom, and red bean paste bun doughs increased by 29.14%, 26.23%, and 43.97%, respectively. This increase suggests that the synergistic effect of SSPS and LD effectively inhibited water migration and reduced the proportion of free water, thereby mitigating the mechanical damage to the gluten network caused by ice crystallization. At the molecular level, chemical analysis showed that the SSPS-LD treatment promoted the conversion of free sulfhydryl groups (-SH) into disulfide bonds (S-S), significantly increasing the disulfide bond content. This suggests that the additives facilitated the polymerization of gluten proteins, enhancing the stability of the network through covalent cross-linking. FTIR spectra further indicated an optimization of the gluten secondary structure, characterized by a transition from disordered random coils to ordered structures, specifically an increase in the proportion of β-sheets. XRD results confirmed that while the crystal pattern remained unchanged, the relative crystallinity of the starch was significantly reduced in the SSPS-LD group, indicating an effective inhibition of starch retrogradation. Microstructural observations via SEM verified that the SSPS-LD group possessed a denser, more continuous, and uniform gluten network, with significantly improved pore distribution compared to the coarse and porous structure of the control group. In conclusion, this study confirms that SSPS primarily enhances water retention through the formation of strong hydrogen bonding networks with gluten and starch, while LD acts as a lubricant and interacts with amylose to form lipid-starch complexes, which hinders starch recrystallization. The synergistic effect of SSPS and LD stabilizes the overall network structure through a combination of covalent and non-covalent cross-linking. These findings provide a solid theoretical basis for utilizing polysaccharide-lipid interactions to control quality deterioration in wheat flour products, and expand the application strategies for functional ingredients in complex food systems.