The utility model relates to an energy-saving air dehumidifier, which comprises a front shell and a rear shell. An evaporator, a condenser and a motor are arranged between the front shell and the rear shell in sequence; a core plate heat exchanger is arranged between an air inlet and the evaporator and consists of combined hollow plastic plates; and thus the cost is low and no electric energy is required. Because the improved core plate heat exchanger is arranged based on the existing air dehumidifier, the heat exchanging capability is enhanced, thereby the heat exchanging area of an air-cooled heat exchanger with a copper tube and aluminum fins is reduced; simultaneously, the cooling capacity of the refrigeration compressor can be reduced to one third; thus the power consumption is decreased; and the utility model saves the energy loss caused by the compressor and the cold exchanger with copper and aluminum tube.