Experimental study of slab CO2 laser bead-on-plate welding and filling wire welding 7075-T6 high strength aluminum alloy of 2.4 mm thickness has been completed. The mechanical properties of welding joints have been analysed. Through analysis of influence of laser power, focal length, welding velocity, working gas and shielding gas on weld shaping and welding stability, filling wire welding of 7075-T6 high strength aluminum alloy is put forward. On the basis of the optimization of feeding direction, feeding angle, feeding velocity and feeding position, filling wire welding of 7075-T6 alloy is completed successfully with slab CO2 laser. The tensile strength of as-welded welds with AlSi12 is 360.8 MPa and with AlMg4.5MnZr 414.6 MPa. The tensile strengths of welds after heat treatment are 404.2 MPa (75 percents of base-metal) and 482.6 MPa (88 percents of base-metal) for AlSi12 and AlMg4.5MnZr, respectively.