The utility model discloses a secondary protection gas hood for welding head, this secondary protect gas hood setting on the external shell of the rifle of welding head, secondary protection gas hood is hollow shell, has seted up secondary protective?gas air inlet and secondary protective?gas gas outlet on it seted up the track groove on the external shell of rifle the one side that is close to the external shell of rifle on the secondary protection gas hood is provided with and is embedded into the locating piece of track inslot. Thereby make secondary protection gas hood can be on the external shell of rifle the reciprocating sliding, the utility model provides a welding head is can be infinitely rot. And the welding is enough implemented at the rot. In -process of aircraft nose to the circular weld around it to the welding rifle physical stamina on it, and secondary protection gas hood also can slide on the external shell of rifle thereupon, assurance the best secondary protection gas air feed position for welding?quality can satisfy nuclear power product 's requirements for quality.