The device comprises an outer mold, an inner mold, a bottom mold, an operation platform, a ladder, a material distributor and a top cover plate, the lower end face of the bottom mold is fixedly installed on the platform, the inner mold is installed on the upper end face of the bottom mold, the outer mold is installed on the outer side of the inner mold, and the ladder is installed on the outer side of the inner mold. The bottom end face of the outer mold is connected with the upper end face of the bottom mold, the operation platform is installed on the side face of the upper portion of the outer mold, the distributing device is installed on the end face of the upper portion of the outer mold, and the top cover plate is installed on the upper end face of the distributing device. The invention further relates to a method for prefabricating the UHPC column formwork. The supporting device is arranged on the inner wall of the inner mold, after concrete pouring is completed, the inner mold is separated from the inner wall of concrete through shrinkage, and the construction efficiency is improved; and the outer mold is spliced through the eccentric quick locking device, so that the splicing precision and the use safety of the outer mold are improved.