In our previous study, red kidney bean polysaccharides (RKP) have been regarded as the functional polysaccharide with glucolipid metabolism regulation activity. The impact of different concentrations of RKP (2, 4, and 6 g/100 g of dough weight) on the water mobility, rheology, and microstructure of frozen dough was examined using low field nuclear magnetic resonance (LF-NMR) and scanning electron microscopy (SEM) in the present study. The findings demonstrated that RKP exerted a positive impact on the water absorption capacity, moisture distribution, and viscoelastic properties of frozen dough. The addition of RKP significantly improved the water absorption of the dough. Specifically, on day 0, adding 6% RKP increased the water absorption rate from 25% to 47% compared to the blank group. Notably, the hardness of steamed bread decreased significantly with the addition of RKP, in addition, its springiness and resilience dependently increased. This offered a theoretical foundation for the use of RKP in the industrial manufacture of wheat-based foods.