The simulation test for the controlled ecological life support system is planned by Institute for Environmental Sciences (IES) of Japan. The purpose of this test is to confirm that in the closed space, the environmental and life support system is normally carried out. The establishments to perform the simulation test has been constructed at Rokkasho-mura village, Aomori prefecture, in Japan. We have been developed “Oxygen Recovery System” which decompose carbon dioxide (CO2) and regenerate oxygen(O2), for the simulation test. The oxygen recovery system consists of a equipment to reduce CO2 using the Sabatier method and a equipment to regenerate oxygen using water electrolysis method (Refer to Figure 1). And this reaction principle is as follows; The carbon dioxide is produced by the respiration of human, animals and plants. The carbon dioxide is reduced to methane and water using hydrogen in the first reaction. The generated methane is decomposed to carbon and hydrogen by thermal decopmposition in the second reaction. Generated carbon is accumulated inside the reaction tube. And the generated water in the first reaction is electrolytically decomposed to hydrogen and oxygen, The generated hydrogen by equations (2) and (3) is circurated to the entrance at the first reactor, and utilized as hydrogen to reduce carbon dioxide.We reported the results of early stage study of this oxygen recovery system, last year1). However, we had some unknown items then because we were just studying about the system.This reports describes about the test result, which performed after the report of the last time, and the studying status of the oxygen recovery system.