The invention provides a mechanical steam recompression system comprising an evaporative condenser, a centrifugal compressor, a screw compressor, an electric water heater, a vapor-liquid separator and a fresh water box. The evaporative condenser communicates with the centrifugal compressor and the screw compressor; a first valve and a drain separator are arranged between the evaporative condenser and the centrifugal compressor; a second valve is arranged between the evaporative condenser and the screw compressor; the centrifugal compressor communicates with the screw compressor; an outlet of the screw compressor communicates with the an inlet of the screw compressor; and the screw compressor communicates with a condensing tube of the evaporative condenser through the vapor-liquid separator. The mechanical steam recompressing system provided by the invention is a mechanical steam recompressing system which has no need to start heat-source steam, can realize a high vapor pressure ratio (Saturated temperature rise of compressed steam) and high vapor flow, and has higher energy efficiency. In addition the mechanical steam recompression system has functions of expanding the application range of conventional mechanical steam recompression systems and realizing industrial energy conservation.