Disclosed are an implantable medical instrument a preparation method thereof and an implantable medical instrument preform for the preparation of the implantable medical instrument. The implantable medical instrument comprises a metal basal body (21) and a polymer film layer (22) covering the surface of the metal basal body (21) and preventing endothelium climbing and covering and also comprises a transitional body (23) which is located between the metal basal body (21) and the polymer film layer (22) and covers at least part of the surface of the metal basal body (21) the transitional body (23) being connected to the polymer film layer (22) and the metal basal body (21). By arranging the transitional body (23) to be connected to the polymer film layer (22) and the metal basal body (21) the polymer film layer (22) cannot easily come off when being implanted into a human body and exerting efficacy in the human body.