Bronze-processed Nb3Sn-based wires reinforced by Nb-rod-method Cu–Nb composite (Cu-Nb/Nb3 Sn) are applicable to react-and-wind (R&W)-processed Nb3Sn coils. The Cu–Nb composite material functions as a reinforcing stabilizer during the superconducting magnet operation. Moreover, it suppresses the damage of reacted Nb3Sn filaments due to applied stress during the manufacturing process such as the prebending treatment, the insulating, and the winding. New Cu–Nb/Nb3Sn wires with high tin bronze (Cu-15.7wt%Sn-0.3wt%Ti) were investigated in the superconducting properties. The round wire of 0.8-mm diameter with prebending strain ϵ pb = ±0.5% demonstrated a non-Cu- J c of 1150 A/mm2 at 12 T and 4.14 K. The rectangular wire of 1.13 × 1.7 mm with ϵ pb = ±0.5% applied from both directions of flatwise and edgewise had a non-Cu- J c of 355 A/mm2 at 17 T. In this paper, we discuss the cross-sectional designs of Cu–Nb/Nb3Sn wires suitable for practical R&W Nb3Sn applications.