Abstract: The article describes the working conditions of the piercing plug, typical forms of out-of-work plugs as well as design of the new type piercing plug. The plug operation process has been set up. Relevant operational practice shows that the new type piercing plug can maintain its fine stream profile and produce smooth regenerated oxide film, which will provent the plug from being out-of-work as a result of flattened plug nose, hence increase the service life thereof.