Abstract: Thanks to the continuous development for nearly twenty years, the process technology of retained-mandrel MPM has been so sound that it has become one of the major seamless steel tube mills being used nowadays. Briefly introduced in this paper are the significant progress made in technical development of retained-mandrel MPM and the characteristics of the retained-mandrel MPM with fewer stands. Also describd here is details about research involving the three-roll adjustable MPM (PQF).