In order to accurately grasp the actual protection effect of molecular sieve in the spot, it is necessary to take the experiment of tritium air (HTO) penetration experiment. With the nitrogen with certain dew point and tritium concentration passing through the molecular sieve with a steady flow and continuous measuring the changes of tritium concentration before and after the molecular sieve as well as the quality changes before and after the penetration, the tritium protection effect of molecular sieve in actual environment was determined. The experimental results show that the tritiated water adsorption effect of anhydrous molecular sieve is the best: the filtration efficiency within 4 h stays above 95% which has high efficiency and stays for a long time; the molecular sieve with 1/3 absorbed water shows a good performance which has a filtration efficiency maintaining above 90% within 3 h. Considering the comfortable degree and filtration efficiency, molecular sieve with 1/3 absorbed water is more suitable for practical tritium protection field.Cited