Abstract: Passive autocatalytic hydrogen recombiners（PAR） are extensively used in the GRE-II,GRE-II+,and GRE-III NPPs.Based on the requirements for key parameters of PAR,such as working features,start and stop threshold,hydrogen removal ability and ignition threshold,the experiment apparatus is designed and constructed which can simulate the NPS severe accident condition and verify the PAR key characteristic parameters under passive condition.Test method is established,and series experiments on the start and stop threshold,starting time,hydrogen removal ability and ignition threshold were carried out.The test results show that different test conditions will lead to differences in PAR parameters,for that reason,only limited methods and conditions are suggested to use to get the unified,measurably quantified PAR key parameters.