As common equipment used in structural piping rolling, three-rolling machine plays an important role in piping prefabrication. How to maximize ergonomics with existing equipment becomes the concern of piping processing enterprises. By analyzing the working principle of three-rolling machine and combining the performance analysis of four basic parameters of maximize rolling thickness, width of rolling plate, the minimum diameter of the rolling diameter and the yield point of the material, a combination restrictions of inter-change of the main technical parameters in rolling process was obtained, and eventually a series of identical transformation equation were got finally. Whether the pipes in different specifications can be rolled by the specific rolling machine was determined through demonstrating specific example.