Non-aluminum alloy brazing sheet type vacuum brazing, identified various elements on Si solder wettability. Add 1 ~ 1.5% Mg, can lead to satisfactory results. Then add a small amount of bismuth, can further improve the solder wettability and reduce the requirements for the degreeCopper Brazing Alloys. The workpiece into the box, and then placed in a vacuum furnace heating cartridge brazing, can significantly improve the quality of brazing. To solder sealing flow can be in the soldering zone plus a small amount of magnesium. In this paper, the role Brazing Alloys  magnesium were studied. Mg vapor through the oxide film is slit, with the aluminum alloy occurs, molten solder along the surface spreading of alloying, and the oxide film is raised, thereby generating wetted. Vacuum brazing solder joint quality can be obtained.