In order to study the influence of doping and strain on the electronic structure and optical properties of [111] crystal-oriented silicon nanowires, based on the generalized gradient approximation (GGA) under the density functional theory system, the first-principles method was used to carry out related calculations. Energy band calculations show that both vacancy doping and element doping introduce impurity energy levels, which change the band gap of SiNWs and form N-type and P-type semiconductor materials. Uniaxial strain further reduces the band gap and strongly enhances the conductivity, but it also modifies the morphology of the energy levels near the Fermi surface. The sudden change in band curvature also affects the conductivity of doped SiNWs. The calculation of optical properties shows that compared with vacancy doping, element doping more effectively changes the dielectric function, absorption coefficient, refractive index and reflectivity of SiNWs, while uniaxial strain weakens the effect of element doping. The tensile strain increases the range and intensity of light absorption, especially in the visible light band, making doped silicon nanowires as a high-quality photovoltaic material, while compressive strain reduces the absorption efficiency in the ultraviolet light band. In the ultraviolet region, tensile strain and compressive strain have opposite effects on the refractive index and reflectivity of doped silicon nanowires, and the effects are the same in the infrared and visible regions The results of this paper provide a theoretical reference for the design and application of optoelectronic devices based on strained and doped silicon nanowires.