By analyzing the phase diagram, four kinds of alloys with different component, Au-24Ag-3.25Si, Au-24Ag-3.25Si-1.5Cu, Au-24Ag-3.25Si-2.0Cu, Au-24Ag-3.25Si-2.5Cu(wt%) were prepared by the vacuum melting method in a medium-frequency induction furnace. The welding experiment was done in a tube type resistance furnace with flow H2 as protective gas, the welding temperature was 550 ℃ and the base plate is pure Ni sheet. The melting temperature was measured by a microscale DTA analyzer and the microstructure and welding performance of the brazing alloy were studied by metallographic and SEM analysis together with X-ray energy spectrum analysis. The results show that the addition of proper Cu can reduce the melting temperature and the interval between solidus and liquidus of the Au-24Ag-3.25Si brazing alloy. The microstructure of the alloy was also changed greatly because of the addition of Cu. There is a new type of solid solution formed, which makes the microhardness of the alloy increased accordingly. The spreading pattern is fine and the wetting angle is small after the Au-24Ag-3.25Si-1.5Cu brazing alloy welding with Ni, whose welding interface structure is almost the same as that without Cu. There is also IMC layer in the interface and the X-ray energy spectrum analysis show that the IMC layer is Ni-Si intermetallic. The addition of Cu will not improve the welding performance of the Au-24Ag-3.25Si brazing alloy with Ni obviously