Abstract: Addressing the shortcomings of the convenient manufacturing processes for small-sized pipes, a new process for the same purpose with the Y type mandrel mill is proposed.Furthermore, based on the FE deformation theory, simulation of the three-dimensional elastic-plastic thermal coupling of the process to roll small pipes with the plane triangular-passed mandrel mill is conducted with the MSC.Marc FE software and the contact-analysis technology, showing the metal deformation process with dynamic pictures and resulting in the strain distribution pattern.The simulation result can be used not only as the basis for application of the said Y type mandrel mil to produce small sized pipes.