Based on the stiffness limitations of the midtower in multitower cable‐stayed bridges, a new stiffening system (tie‐down cables) is proposed in this paper. The sag effects and wind‐induced responses can be reduced with the proposed system because tie‐down cables are short and aesthetic compared with traditional stiffening cables. The results show that the stiffening effect of tie‐down cables is better than that of traditional stiffening cables in controlling the displacement and internal force of the bridge based on a static experiment and finite element analysis. Therefore, the proposed system can greatly improve the overall stiffness of a bridge, and its stiffening effect is better than that of traditional stiffening cables in controlling the displacement and internal force. The results provide a reference for the application of such systems in practical engineering.