The invention relates to a high-efficiency large-scale band sawing machine which comprises a machine body, upright posts, a lift cylinder and a saw frame, wherein a feeding bracket is arranged in front of the machine body; the feeding bracket is provided with two linear guide rails; the back end sections of the two linear guide rails extend out of the feeding bracket and are overlapped on the machine body; a movable lower chassis is arranged on the linear guide rails, and is connected with and driven by a drive unit which is arranged on the machine body; an upper rotating disk is arranged above the lower chassis; the bottom surface of the upper rotating disk is annularly provided with a plurality of supporting rollers which contact the lower chassis; the upper surface of the upper rotating disk is provided with a workpiece clamping device; a rotation drive unit, which drives the upper rotating disk to rotate, is arranged on the bottom surface of the lower chassis; and a rotating shaft, which outputs power, extends upwards out of the lower chassis and is connected to the inside of the upper rotating disk. The invention can horizontally move and rotatablely saw the large-scale workpiece by clamping the workpiece on the upper rotating disk, thereby greatly enhancing the sawing precision and efficiency.