Abstract: The radiolysis of polystyrene tri-methylamine resin in the medium of limited air, me-thanol, 80% methanol-1M HNO3, 1M HNO3 and water are compared. The results show that different changes in the various chemical and physical properties of the resin are induced by different medium. Minimum change of exchange capacity in the air is observed, suggesting that the existence of oxygen might play a protective role. When radiation dosage is less than 1×106 Gy, little difference of exchange capacity in various medium is observed. When the dosage is more than 1×106Gy, the changes are found as follows: CH3OH≥80% CH,OH-1M HNO3>1M HNO3>H2O. This fact may be the result of the different swelling states of the resin after irradiation. The swelling of the resin in the water after irradiation decreases in this sequence: CH3OH>air≥80% CH3OH-1M HNO3>H2O>1M HNO3. The order of loses of weight are measured as follows: CH3OH>H2O>80% CH3OH-lM HNO3>1M HNO3. The gaseous products of irradiated resin are determined. It is considered that the gases of irradiated resin are mainly contributed by the medium.