Due to the connection problem of Cu/W during the rolling process of tungsten plate, dissimilar metals Cu/W are welded by Tungsten inert gas(TIG) welding.In the case of coating SiO2 and uncoating SiO2 activating flux,the spot welding of W overlapped by Cu was conducted,respectively,the appearance of spot welding,cross-section,microstructure and tensile strength of joints were analyzed,respectively.The results indicate that top surface of the welding spots uncoated SiO2 are convex and irregular,many holes at the interface,in the case of coating SiO2,the center of welding spot appears round pits,the number of holes at interface reduce.Interdiffusion occurs between Cu and W,the interface of samples coated with SiO2 is more tightness than the uncoated. When the welding current is same,the strength of joint coated with SiO2 are higher than the uncoated,in the two cases of welding ,fracture exists a large different.