When welding on a container, the medium in the container will easily burn under the action of high temperature arc,and cause the container explosion,casualties and equipment damage. Therefore,the reliable welding technology measures must be adopted to avoid the accident when welding on a container. The welding of a throttle on a transformer oil tank is mainly introduced. Because the medium in the transformer oil tank can not be replaced,the welding is completed by a method of combination of replacement and non replacement with pressure. During the welding process,the weld interpass temperature and the temperature of nearby oil tank wall are strictly controlled,and lower the temperature of welds in time to avoid an accident cause by the high temperature of the container wall.