The invention relates to large-scale methanol multi-effect energy-saving rectifying device and process. Main equipment used in the process sequentially comprises a pre-rectifying tower, a second rectifying tower, a pressurizing tower, an atmospheric tower and a recovering tower, wherein the tops of the second rectifying tower, the pressurizing tower and the atmospheric tower are respectively usedfor discharging refined methanol, the top of the recovering tower is used for discharging fusel oil, and the bottom is used for discharging purified wastewater. Because one rectifying tower is additionally arranged, and the process parameter of each tower is adjusted, two methanol multi-effect energy-saving rectifying processes by five towers are obtained, the effective energy loss is reduced, thereby energy consumption is reduced. In addition, the diameter of each tower is reduced, the amplification effect of relevant equipment, caused by the oversize diameter of each tower, is greatly reduced. The process has the advantages of reasonable design, the energy is fully and reasonably utilized in the process, the energy consumption of the whole device used in the process is reduced by 20%-30% higher than that of the device used in the traditional double-effect process, and the purity of a product reaches the American AA-level standard.