For the problem that the existing Tarnovsky wide stretching model cannot obtain the roll forging wide stretching coefficient of forgings with large shaft-to-diameter ratio such as epee swords during the design process of roll forging mold, an experimental study on flat forging of forgings with large shaft-to-diameter ratio was carried out, the experimental wide stretching data of flat forging was analyzed,and the the Tarnovsky wide stretching model was supplemented. Based on the suppled model, a 14-pass roll forging stretching mold for a certain type of epee sward bar was designed, the plastic finite element model of the roll forging stretching process of sword bar was established, and the roll forging stretching process of the 5th pass of sword body was simulated. Finally, the metal flow law in the roll forging deformation zone was obtained by strain analysis and stress analysis. The results show that the wide stretching mainly comes from the compression deformation zone in the height direction of forgings, and the wide stretching predicted by the finite element model is in good agreement with the equivalent wide stretching obtained in the flat forging experiment. Thus, the research results can be used to guide the design of roll forging molds and the optimization of roll forging process for forgings with large shaft-to-diameter ratio.