Abstract: A sort of Passive Autocatalytic Recombiners（PAR）,including function,component,site arrangement,in-service test method and period,used in Qinshan Second Nuclear Power Plant Unit 3 and 4,were introduced.Efficiency comparison tests of four groups of initial catalytic plates and that used for one refueling cycle（1C） were conducted.Rust and oil stain issues,which were prone to occur during the commissioning and operation process,impacting on the hydrogen reduction efficiency of catalytic plates were put to test and analysis.The results show that,compared with the initial samples,the hydrogen depletion rate of the catalytic plates after 1C is slightly decreased with the influence of oil stain and dust.A small amount of rust and oil stains does not have a significant impact on the efficiency of the catalytic plates.However,rust is liable to cause the catalytic plate to be perforated and to be damaged.Flue gas generated in the test of the oil stain plates is easy to interfere with the dehydrogenation process.