We have developed a method of compensation for fluctuations in beam intensity that may occur during measurement of Pion, the ion-recombination correction factor, by the two-voltage technique. The method requires signals proportional to beam intensity during measurement. We used a parallel-plate ionization chamber, whose Pion was known, and a vacuum chamber to obtain signals that were proportional to the beam intensity. Experiments were conducted using pulsed proton beam providing doses that ranged from 0.16 to 0.01 cGy/pulse. The value of Pion of a thimble ionization chamber was measured. With these measurements, the validity of the method which we proposed for pulsed beam was verified experimentally.