Half-metallic, optical and band offsets properties of CrSb/KCl [0 0 1] interface have been calculated within the density functional theory (DFT) framework using FP-LAPW + lo method. We found that the CrSb/KCl [0 0 1] heterojunction retain perfect half-metallic character with 0.95 eV and 1.5 eV spin flip gap at spin down, using GGA and mbj approximations, respectively. The 0.03 meV electrostatic potential gap between CrSb film and KCl substrate demonstrate that the CrSb film is the good spin electron source for injection to the KCl film. The optical coefficients such as real and imaginary parts of dielectric function, reflection, refraction, extinction and energy loss function indices have been shown the good optical response in the visible area. The band offset parameters of CrSb/KCl [0 0 1] interface are of the type-I model with great amount of Phi(B) and chi potentials.