The invention discloses a method and fixture for welding high temperature alloy and cupronickel. A brazing filler metal consisting of powdery gold 20, nickel, chromium, iron, silicon and boron, or consisting of platinoid copper, manganese, cobalt and nickel is used for welding. The brazing filler metal is coated or arranged between a cupronickel piece and high temperature alloy, and the peripheryof the bonding surface of the cupronickel piece and the high temperature alloy is coated with a red stop-off agent and is pressed tightly by a fixture. A brazing filler metal welding piece which is pressed tightly by the fixture is put in a vacuum furnace, and then the processes of vacuumizing, heating and brazing are performed. Since the brazing filler metal consisting of copper, manganese, cobalt and nickel has the characteristics of high strength, good corrosion resistance, low price and high weld joint quality, and the brazing filler metal consisting of gold 20, nickel, chromium, iron, silicon and boron has the characteristics of good ductility and strong wetting function, respective pressing is omitted the process of brazing, thereby achieving good molding quality of the weld joint. Since the brazing elements of the two brazing filler metals used in the brazing process have the alloying effect on the two materials to be connected, the brazing joint has large spreading area, the joint is high in strength, and the quality of the brazing joint meets the requirement.