The invention relates to a method and a bent tungsten electrode for automatic backing welding of pipes of a nuclear power station. The method comprises the steps of assembling the grooves of the pipes before welding; and using the bent tungsten electrode to perform backing welding to the grooves, wherein the bent tungsten electrode comprises an electrode main body, one end of the electrode main body is a sharpened tip part, the tip part is bent relative to the electrode main body to form a bent part and the top end of the bent part is arranged on one side of the axis of the electrode main body. By using the bent tungsten electrode to perform backing welding to the assembled grooves, the requirement on the groove assembling dimension is reduced, the technical difficulty is reduced, the risks that a root face is penetrated and the tungsten electrode collides the side walls of the grooves during welding can be reduced, the situations such as damages to the grooves of the pipes and tungsten sticking are reduced, the welding construction period can be shortened and the welding quality is improved.