Abstract: In this paper, the effects of different kinds of activating fluxes on appearance of weld was analysed during the electron beam welding(EBW)of nickel-base super alloy GH4169, oxides had deep influence on welding depth and weld formation of both sides of plate, while fluoride had no influence.And on base of it, activating fluxes which can greatly improve weld shape and surface quality of EBW are obtained by combination and optimization.The reason of improving appearane of weld is that, with activating fluxes change surface tension gradient in the weld pool, then affect the pattern of the fluid flow, consequently form narrow and deep, well shape weld.The results show that activating electron beam welding can improve appearane of weld and eliminate some surface defects such as undercutting, which is very useful during thin plate EBW.