Abstract: The paper involves a deep study of mechanism and control methods of "bulging" formation of the continuously roiled steel tube and a comprehensive introduction to the recent ressearch progress concerning formation and control of "bulging" made by a number of manufacturers in W. Germany and Japan. With a new control method for "bulging" developed by the Steel Tube Works of Baoshan Iron & Steel Complex, "bulging" occurred on tube rear seetion could be almost eliminated, meanwhile the wallthickness on rear "bulging" section, could be controlled as the same as that of the middle section, and even smaller.