The Nb3Sn layer growth rate, the upper critical field and the critical current density in high fields of the composite‐processed Nb3Sn are greatly enhanced by the titanium addition to the niobium core. This addition yields aJc(Nb3Sn layer) value of over 1×105A/cm2at 15 T. After the reaction, large amount of titanium is incorporated into the Nb3Sn layer. The optimal amount of titanium addition to the niobium core is about 2 at. %. The Nb‐Ti/Cu‐Sn composite wire seems to be quite promising for applications in magnetic fields up to at least 15 T.