We found that critical current Ic, upper critical field B c2 and critical temperature Tc are greatly enhanced by pre-bending treatment for bronze route Nb3Sn superconductors, called the pre-bending effect. The superconducting properties of Nb3Sn superconductor are sensitive to strain. However, a pre-bending treatment of the Nb3Sn wire enhances the properties. This is because the treatment causes relaxation of the residual strain in the Nb3Sn layer in the wire. Interestingly, the pre-bending effect also makes the Nb3Sn wire stronger against strain. By using this effect, the react-and-wind (R&W) method is expected to be applicable for the fabrication of the Nb3Sn superconducting coil. In this paper, the development of Nb3Sn coils made by the R&W method with the pre-bending effect is described, and the efficiency of the cable assembled by the reacted Nb3Sn strands is discussed.