Abstract: Analyzed here in the article are causes for the annular scratch defect of the mandrel as developed during rolling process of the mandrel pipe mill,and accordingly proposed are relevant preventative actions.The consistent rolling operation for a longer mandrel service span,and better tube quality can be ensured by means of such actions as measuring the overlap between the rolling centerlines of the mandrel mill and the extracting mill with the laser tracker,dynamically,timely and precisely controlling the closing device of the mandrel steadier,using the V-shaped supporting roller as the centering one,and adding the mandrel escaping function to the electric control system,etc.And the last method as above mentioned for enhancing the roll level of the mill is worth popularizing.