Abstract: Based on the production of small-sized precision seamless steel pipes, the Φ114 mm PCM mini-flow mandrel mill operation line for precision seamless steel pipes is detailed here in the paper, involving equipment type selection and technological characteristics as well as the actual production circumstances.The operation practice shows that using the 3-stand, 2-roll mandrel mill to produce hot-rolled precision seamles steel pipes in small lots has brorght about remarkable advantages in product quality, operation cost, energy-saving and enviornment protection, investment operation, and more other advantages like flexibility in production arrangement, and the equiment that is easy to be operated to reach the target output.