The geometry of pure AlN, (La, Y) single-doped and La-Y co-doped AlN superlattices was optimized by the plane wave ultrasoft pseudopotential method based on density functional theory. The band structure, density of states and optical properties of the system before and after rare earth elements (La, Y) doping were calculated. The results show that the undoped AlN is a direct band gap semiconductor, and the band gap value is Eg=4.237 eV. The density of state is mainly contributed by electron orbitals of Al-3p and N-2s.After doping, the band structure property is changed, the band gap value reduces, the band curve is denser, and the total density of states moves down as a whole.In terms of optical properties, the doping of rare earth elements improves the static dielectric constant and light absorption performance, enhances the refractive index and reflectivity, and reduces the probability of electron absorption photon and energy loss.Among them, La-Y co-doped system changes obviously.