Ti-Nb alloys are widely used in aerospace, medical, and superconductivity applications because of their excellent properties, such as shape memory effects, corrosion resistance, nontoxicity, and superconductivity. Ti-Nb alloys with compositions ranging from 35 wt.% to 55 wt.% were prepared via vacuum arc remelting and hot rolling processing to elucidate the influence of the Nb content on the microstructural evolution and mechanical behavior. The results demonstrate that the microstructure of the solution-treated Ti-35Nb alloy consists of equiaxed grains with a grain size of approximately 50~100 μm, accompanied by stress-induced martensite within the grains. The tensile curve exhibits a distinct double-yield phenomenon, with an ultimate tensile strength of 650 MPa but a relatively low yield strength of 225 MPa. As the Nb content increases to 45 wt.%~55 wt.%, the alloy undergoes significant grain refinement, coupled with enhanced β-phase stability, which suppresses martensitic transformation. Consequently, the tensile curves display no double-yield behavior, and the strength and ductility of the alloy match well. The incorporation of Nb improves the comprehensive mechanical performance through three mechanisms: β-phase stabilization, solid-solution strengthening, and grain refinement.