To investigate how natural inulin (FI) influences the quality of heat-induced beef myofibrillar protein (BMP) gels, BMP gel systems were prepared with graded FI concentrations (1%, 2%, 3%, 4%, and 5%). Texture analysis (TA), low-field nuclear magnetic resonance (LF-NMR), rheological measurements, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR) were used to systematically characterise changes in gel properties, water migration and distribution, microstructure, and protein secondary structure. The results showed that the improvement in gel quality produced by inulin was concentration-dependent. FI at addition levels of 1–2% promoted the ordered intermolecular cross-linking of beef myofibrillar proteins, thereby facilitating the formation of a homogeneous and compact three-dimensional gel network, as confirmed by SEM and CLSM observations. Notably, 2% FI was identified as the optimal addition level for the BMP gel system. Compared with the control group, this treatment produced the highest relative β-sheet content (82%) among all groups, optimised the internal water distribution of the gel by reducing the proportion of free water, enhanced the water-holding capacity of the gels (p < 0.05), and preserved the elasticity-dominated solid-state characteristics of the BMP gel system (tan δ < 1), indicating that FI improved gel strength without changing its fundamental properties. These findings provide an important theoretical basis and practical technical parameters for the development of functional beef products with both desirable texture and high dietary fibre content.