Abstract: Development of the structure of the 3-roll mandrel pipe mill is described here in the article.And a comparative analysis is made， involving the similarity and otherness of the three roll-change types， i.e.， axial roll-change，side roll-change and bilateral roll-change.Also elaborated are the main technical parameters for the three roll-change methods，and the differences between roll stand of the PQF mill and that of the FQM mill.From suitability point of view，for small-size steel pipe mills either axial roll-change method or side roll-change method is a proper selection，while for large-sized tube mills only axial roll-change method is preferred.