Abstract: This paper presents an improved design of the O₂ consumption simulation device used for verifying the Environmental Control and Life Support System before the launch of the manned spacecraft. To tackle the problems found in the first set of the molecular sieve oxygen consumption simulation device such as the poor air tightness, the relatively large cabin pressure fluctuation in the process, and the low oxygen production efficiency, this paper puts forward an improved design scheme including a reselection of the air compressor model, a revised design of the equipment pipelines, and an comprehensively optimized work flow. The test results show that the upgraded system can meet the air tightness requirement of the space station ground test; the influence of the oxygen consumption process on the cabin pressure is reduced nearly by two orders of magnitude, and the time to establish a desired oxygen consumption concentration is shortened from half an hour to five minutes, which provides a guarantee for the ground verification of the Environmental Control and Life Support System.