Abstract: In this study, we investigated the treatment of insoluble dietary fiber from mushroom stems (MSIDF) using steam explosion technology. We added different amounts of modified insoluble dietary fiber from mushroom stems (S-MSIDF) (2%, 4%, 6%, 8%, 10%) to tapioca starch and analyzed how they affected the physicochemical properties, structure, and digestive characteristics of tapioca starch. The results indicated that steam explosion modification enhanced the water-holding capacity, swelling capacity, and glucose adsorption capacity of MSIDF. Furthermore, with the increase of S-MSIDF addition amount (2%~10%), the effect on the properties of tapioca starch became more significant. The addition of 10%S-MSIDF significantly decreased the peak, trough, and final viscosities (P<0.05), as well as the breakdown and retrogradation values of tapioca starch, while it also increased the gelatinization temperature and delayed the gelatinization process. Enthalpy change (ΔH_g) reduction exerted a certain inhibitory effect on short-term starch retrogradation. The storage and loss moduli (G′ and G′′, respectively) decreased, while the loss tangent (tanδ) increased, indicating enhanced fluidity. 10% S-MSIDF supplementation significantly reduced tapioca starch gel hardness, viscosity, elasticity, and chewiness (P<0.05). 10%S-MSIDF imparted a denser network structure to tapioca starch gel, with the primary interaction between the two being hydrogen bonding. 10%S-MSIDF significantly reduced the rapidly digestible starch content (P<0.05), while increasing slowly digestible and resistant starch levels. Therefore, steam explosion modification could alter the structure and properties of the insoluble dietary fiber from mushroom stems, thereby altering its interactions with tapioca starch. These findings provide a theoretical basis for applying insoluble dietary fiber from mushroom stems in starch-based products.