The modification of SrTiO₃ materials by doping Nb⁵⁺ ions in B-site is studied through using the first-principles method to calculate the electronic structure, optical properties, mechanical properties and thermal properties at different Nb⁵⁺ doping concentrations. The calculation results show that as the doping content of Nb⁵⁺ increases, the lattice parameters increase. After being doped with Nb⁵⁺, SrTiO₃ changes from an indirect band gap compound into a direct band gap compound. Doping Nb⁵⁺ can reduce the reflection coefficient, absorption coefficient, and energy loss of SrTiO₃ material, which can be used to modify its optical properties. Additionally, the brittleness of SrTiO₃ material is improved through doping Nb⁵⁺. As the doping content of Nb⁵⁺ increases, the elastic modulus of the material hardly changes, the shear modulus and Young's modulus decrease, the Poisson's ratio increases, and the Debye temperature decreases, and both the lattice thermal conductivity and the theoretical minimum lattice thermal conductivity decrease as well.