Abstract: Compared are the deformation principles and the manufacturing practices of the longitudinal-rolling process and the cross-rolling process for the seamless steel tube,and also analyzed is the superiority of the crossrolling process.The main theoretic aspects are studied,involving the space geometry concerning the groove,the stress and strain of cross-rolling,the cross-rolling kinematics,and the calculation method for rolling force,etc.The types and characteristics of rotary-rolling pipe mills are elaborated.Furthermore,addressing the problems as staying with currently-used cross-rolling processes,relative improvement measures and the development direction are proposed, which introduces a new type rotary-rolling pipe mill.Based on relevant analysis, it is concluded as follows.Problems such as limitation of the deformation ability and defective surface quality of the tube,etc.as associated with present hot cross-rolling mills are expected to be tremendously reduced by means of optimization of the cross-rolling process and modification of the cross-rolling equipment so as to enhance the general level of the cross-rolling technology for seamless steel tubes.From the point of views of project economy,suitability and practicality, as a rolling process for hot-rolled seamless steel tubes, the new type rotary-rolling pipe mill as mentioned in the paper is worth applying and developing.