Abstract: The atmosphere ionization induced by α-rays was experimentally studied using fission ionization chamber with two plane electrodes. The influences of distance between the two electrodes and the position of radioactive source in the chamber on the experimental results were explored. The results show that the measured ion-pairs increase slightly with the distance between the two electrodes as the distance shorter than the double length of α-ray flying in the air. The position of radioactive source in the chamber has no remarkable influence on the measurement. The experimental results of ion-pairs induced by α-rays in the air agree well with that from the theoretical calculation.