The utility model relates to a bimetal composite pipe liquid-expansion forming mold. The bimetal composite pipe liquid-expansion forming mold is characterized by comprising a mold sleeve, a follow-up expansion sleeve arranged on the mold sleeve, and a protective cover fixed to the mold sleeve; the follow-up expansion sleeve comprises a sealing ring, a locating device, a mold core, an inner sealing ring and a radial sealing guide block; the mold core is arranged on the mold sleeve and can move axially along with the mold sleeve; the inner sealing ring is arranged on the mold core; the radial sealing guide block is connected to the inner sealing ring; the sealing ring is arranged on the mold core and used for sealing a gap at the position where the mold sleeve and the mold core is connected; the locating device penetrates through the mold sleeve and is installed on the mold core. An inner layer pipe of a composite pipe is tightly combined with an outer layer pipe under the action of ultrahigh pressure liquid; the bimetal composite pipe liquid-expansion forming mold has the advantages of being good in sealing performance, simple in structure, convenient to control, high in reliability and low in cost.