Abstract: Introduced in the paper are the technological achievements as made by Taiyuan Tongze Heavy-duty Industries Co.,Ltd.,and concerning the manufacture and design of equipment of the mandrel mill process for hot-rolling of seamless steel pipes,covering employment of the hydraulic screwdown system as featuring high accuracy and dynamic setting function for the mandrel mill,and design and development of the new type Φ140 and Φ180 mm series 2-roll,6-stand mandrel mills (MPM) as well as the 3-roll,5-stand mandrel mill with lateral roll-change function (TRCM).Relevant operation results of the mills show that the rolling tolerances of the mills are enhanced due to a number of modification measures involving development of the control system,the pass design and optimization of the mechanisms,etc.,which is regarded as a considerable contribution to speeding up the production localization of the mandrel mill.