The invention discloses a transfer platform used for ship cargo transshipment and a building method thereof. The transfer platform comprises a main body part and a caisson foundation. The main body part comprises a cargo hold used to store cargo, a shipment device used to load the cargo in the cargo hold to a ship, and an unloading device used to unload the cargo on a ship into the cargo hold, anda bow ballast tank used to adjust floating conditions of the main body part. The caisson foundation comprises at least a cavity, and the cavity is used to adjust floating conditions of the caisson foundation through injecting ballast water into the cavity. The transfer platform is a bottom-supported platform. The transfer platform improves capability of adverse environment resistance and improveslightering efficiency.