It is shown experimentally that three major factors must be considered to obtain a CO2 laser with long life-time.They are:1)elimination of slow gas leakage,2)selection and oxidation of electrode material,3)decreasing the decomposition of CO2 molecules.We have done in the following ways:laser tube is not dried but filled with water vapor,the electrode material must be degassed in vacuum and oxidized by filling oxygen gas.When pure silver electrode is employed,gas mixtures constitutions of 1)CO2-N2-He-Xe-H2O,2)CO2-CO-He-Xe-H2O,3)CO2-N2-CO-He-Xe-H2O, the operation life-times are respectively 1)10,476 hours,2)9185 hours(still in operation),3) 9207 hours(still in operation);while pure nickel electrode is used with CO2-N2-He-Xe-H2O gas mixture,operation life-time is only 1644 hours.