Based on the first principles pseudo-potential plane-wave method, geometrical structure, electronic structure, and optical properties of V-Al co-doped CrSi2 are calculated. The photoelectric properties of un-doped CrSi2, and co-doped with V and Al, and single-doped with V or Al are compared in detail. The results show that: co-doped with V and Al, the lattice constant a, b, and the volume of CrSi2 is increased. V-Al: CrSi2 is a p-type indirect semiconductor, and the energy gap is 0.256 eV, which is between the gap value of CrSi2 with single-doping V or Al. The density of states near the Fermi energy is mainly composed of Cr-3d, V-3d, Si-3p and Al-3p orbital hybridization. Compared with pure CrSi2, the static dielectric constant and the refractive index of CrSi2 are increased with co-doping of V and Al. A new transition peak of εi(ω) is appeared at the lower energy region. Near 5 eV, the transition peak intensity of εi(ω), the absorption coefficient, and the photoconductivity is decreased, respectively. The absorption edge generates a red shift, and the average reflection effect is decreased. Doping with V will weaken the electron transition in Al single-doped CrSi2. V-Al co-doped can critically regulate the band structure and the optical properties of CrSi2.