Abstract: Elaborated in the article are the processes to produce hollow hexagonal bar steel.And a new process for this purpose is proposed, i.e., a piercing-sizing formation process.Relevant simulation software is used to simulate the formation step of the formation-by-sizing process.The simulation result shows that it is a practical method to produce the hollow hexagonal bar steel by means of directly using the sizing mill, i.e., the piercing-sizing formation process.In case of producing hexagonal hollow bar steel with the said formation process, suitable pass dimensions must be adapted for the formation stands of the sizing mill, while the elongation rate and pass dimensions of each individual formation stand must be in compliance with the requirement for proper metal flow.For the said elongation rate, 1.15~1.25 is a satisfactory selection.