Geometrical structures of Cr doped and Cu-Cr co-doped 32-atoms supercell of AlN were optimized with first principles density functional based on full potential augumented plane waves and generalized gradient approximation (GGA). Lattice constant, band structure, electronic density and optical properties were calculated. It indicates that Cr-doped and Cu-Cr co-doped AlN are both half metallic, their band gaps become narrower. Cu-Cr co-doped AlN system has stronger spin polarization effect than Cr doped, and exhibits fine ferromagnetic. Range of optical absorption becomes broader with doping. Co-doping enhances long-wave absorption and energy loss decreases obviously.