Abstract: For the product mix expansion-aimed modification of the rolling frame of the 3-roll mandrel mill, a design scheme is proposed aiming at reducing the modification investment and minimizing the modification involvement.Following the design proposal, the floating end and the fixed end of the roll bearing shall be exchanged, and meanwhile the size of the positioning pin for mounting the floating bearing seat shall be reduced.Thanks to checking/ratification of relevant mechanical parameters and the equipment space positions, it is proved that this very modification idea is satisfactory to the requirements of the general product mix expansion-aimed modification of the mill, and in possession of such advantages as low investment and small modification involvement.