The crystal structure of solar material ZnSe and CuXSe2 (X=Al.Ga, in) has been optimized firstly by using the pseudopotential plane wave basis set of density functional theory, studied the lattice parameters, bond lengths, and forecasted the CuXSe2 band gap and optical properties. The results indicate that the band gap decreased in accordance with Al→Ga→In, but the lattice parameters and deformation parameters increased.The optical properties of dielectric function, absorption coefficient, reflectivity and photoconductive rate have been analised and foud that the strongest peaks of the absorption coefficient are in the ultraviolet region. The optical properties increased in accordance with Al→Ga→In successively in three crystals.