Abstract: Addressing the problems as staying with the 20CrMoNbVTiB CC billet in Steel Grade 110S such as poor plasticity,high resistance against deformation during rolling process and a lot of difficulties as occurring in the rolling operation,the technological process of the Φ180 mm mandrel pipe mill is discussed and optimized,involving a number of measures,including increasing the circular furnace temperature,lowering the rpm of the piercer,adapting large feeding angle,using after running-in roll,adjusting MPM rpm,and re-heating the shell in the MF furnace prior to sizing process,etc. Thanks to the above mentioned optimization of the mill,the whole hot-rolling process is performed very well.Moreover the plug service life is greatly prolonged,the repair rate is remarkably reduced,and the yield is enhanced from 81.6% up to 91.5%.