Abstract: The influences of vacuum-desorption on the performance of small-scale oxygen concentrator by pressure swing adsorption (PSA) were studied experimentally．The effects of operating parameters，such as inlet pressure of adsorber，oxygen flux，pressure equalization time on the oxygen concentration in the product were investigated in both vacuum and atmospheric environments．The results show that vacuum-desorption was helpful to increasing the oxygen concentration and decreasing the start-up time. Less effects were produced by inlet pressure，oxygen flux and pressure equalization time on the oxygen concentration in vacuum environment than in atmospheric environment，although the desorption behavior is the same in both environments.