Abstract: As one of the key mill units of the seamless steel pipe rolling plant,the centering roll steadier clamps the plug bar-shell piece during the piercing process so as to enhance the rigidity of the piercer plug and bar prevent any deviation of the plug bar-shell piece from the normal rolling line,which may consequentially lead to internal bore eccentricity of the shell,and thus lessen the product quality. A calculation method for designing a new type of leakage centering roll steadier is elaborated here in the paper,i.e.,using both the construction technique and the Inventor 3-D sketch software to make the centering accuracy of the said centering roll steadier as designed up to 0.03 mm when the opening rangs is of Φ100~500 mm.