Abstract: To further optimize the product mix of the Ф180 mm Mini-MPM,the Ф210 mm billet is added in the original Ф180 mm and Ф270 mm billet range,and accordingly,the 204 mm pass series is developed to cope with the manufacturing operation of the mill. Elaborated in the article are the idea and design process concerning the R & D of the said new passes. The one-year long operation and the lot-production of the mill demonstrate that the manufacturing process with the Ф210 mm billet has got normalized, and both the dimensional accuracy and outer surface quality of pipes as rolled are up to the requirements by the customer,which means that the development of the 204 mm pass series is successful.