Abstract: Resistance spot welding is used to weld LY12 aluminum alloy /TC4 titanium alloy with Ni particles by 3-phase DC resistance welding machine. The results show that the optimal parameters of welding joint with Ni particles are as follows. The electrode pressure is 3.03 kN, the welding current in the first pulse is 7.5 kA, and the welding time in the first pulse is 10 cyc (1 cyc=0.02 s). The welding current in the second pulse is 12.1 kA, and the welding time in the second pulse is 45 cyc. The welding current in the third pulse is 7.5 kA, and the welding time in the third pulse is 10 cyc. The maximum tensile shear strength of the welding joint with Ni particles is 7.12 kN. The microstructure of aluminum alloy side of nuclear fusion is coarse columnar crystal,and the microstructure of titanium alloy side of nuclear fusion is coarse acicular martensite. The main component of the IMC layer is a layer of 1～2 μm thick planar NiAl3 which is close to the aluminum side, and white massive TiAl3 in scattered distribution between titanium alloy and aluminum alloy in the welding joint with Ni particles.