The optimized condition has been researched, for welding super alloys (Inconel 600, Inconel 625 and Haynes 230), which are used for liquid thruster of an artificial satellite. In the experiment of “bead-on-plate”, these materials are welded using continuous Nd:YAG laser and electron beam. The penetration depth and bead width are measured by optical microscope. The hardness of 1mm depth from welding surface is measured by micro Vickers hardness tester. The tension is tested for measuring the strength of welding part. The tension strength of welding specimen using the Nd:YAG laser is compared with that of the welding specimen using the electron beam.