A wet-type exhaust gas desulfurization system comprises a reservoir for trapping an absorbing solution which has absorbed SO.sub.2 from exhaust gas; an absorbing solution circulating tank disposed directly under the reservoir; a plurality of bottom pipes which are installed at the bottom of reservoir and extend downward into the absorbing solution in the circulating tank and whose lower end is open, or drop pipes which depend into the absorbing solution and whose lower ends are open; and air supply pipe at least one end of which is open to the atmosphere; a pipe for discharging the air above the surface of absorbing solution onto the surface of solution in the reservoir; and a pipe for supplying the absorbing solution in the circulating tank to a spray nozzle at the upper part of the absorbing tower.