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We investigated the superconducting properties of Nb3Sn formed through the diffusion reaction between Nb and Ag-Sn alloys, including Ag-9at%Sn ductile fee phase and Ag-(12-16)at%Sn ductile zeta phase alloys, and Ag-24at%Sn brittle epsiv phase alloy. We fabricated single-core and multi-core composite wires by the rod-in tube and powder-in-tube processes. The composite wires were heat treated at 650-900degC to form Nb3Sn filaments. With increase of Sn content in the Ag-Sn alloy cores, the superconducting properties of the Nb3Sn composite wires were improved. Tc and Bc2 (4.2 K) values for the Nb/Ag-Sn wires are similar to those for the Nb/Cu-Sn. However the Ic values are relatively small, due to their very thin Nb3Sn layers below 0.4 mum. Ag is apparently not effective to increase the formation rate of Nb3Sn layer. By using the 200- and 40000-core wires, Tc and Bc2 (4.2 K) values were increased by 0.5-1 K and 2-5 T, respectively for these multifllamentary wires, while from 10 to 500 times larger Ic (4.2 K) were obtained for the wires. The typical values for Tc and Bc2 (4.2 K) are 16.5-17.7 K and 16-21 T, respectively. The addition of 5at%Cu to Ag-Sn alloys improves their superconducting properties.