Abstract: The paper discusses the continuous rolling characteristics and special deformation law of the two-roll rotary rolling pipe mill, analyzes the causes for small deformation capacity of the Accu-roll mill and the approach to increasing the mill's deformation capacity. Also analyzed here is why the two-roll cross-rolling pipe mill with short plug has the maximum deformation capacity as in terms of rolling mill proper, covering the principle for defining the wall reduction and the law of wall reduction distribution with respect to each pass. With relevant example, design of continuous rolling groove and deforming tools are described, involving principle, steps, scope as well as area calculation method for both inner and outer wall-reducing zones.