Abstract: Taking the production site work conditions of the gas cylinder-purposed pipe into consideration，the FE model for the tube deformation during the 3-roll mandrel mill process is set up with the 3-D FE model analysis technology， and then is used to compare the changes of the tube-mandrel contact angle and the relationship between the tube-mandrel contact angle，and the reported tube internal scratch rate as occurring before and after the pass optimization. The comparison result shows that the tube-mandrel contact angle acts as one of the important factors as affecting the said scratch rate；and therefore the said internal scratch rate is expected to be reduced by means of increasing the disengagement proportion of the mill pass，particularly using proper tube-mandrel contact angles for the No.1 and No.2 roll stands.