The role of Ag sheath on the formation of a 2223 phase in Ag-sheathed Bi-Pb-Sr-Ca-Cu oxide tapes was investigated. It was found that the Ag sheath promoted the formation of the 2223 phase through the extension of the temperature range between its partial melting and decomposition as well as through the ease of the control of the atomosphere in the Ag sheath. Furthermore, the Ag sheath was recognized to act as an effective substrate for the formation of the well-developed texture structure.