Vacuum pressure swing adsorption (VPSA) for oxygen generation is a complicated dynamic process. Understanding the flow characteristics is essential for the design and improvement of radial flow adsorber. A two-dimensional radial flow adsorber model of VPSA for oxygen generation was established based on the Fluent porous medium model with user defined functions. The flow characteristics of the first and second cycle in radial flow adsorber were analyzed. The effects of particle diameter, the perforated-plate opening ratios and the cross section ratio of central channel to outer channel were discussed. The results showed that the flow distribution and adsorption efficiency of radial adsorber were affected by the volume of both the central channel and the outer channel, which needed to be carefully considered when designing. The concentration and recovery rate of oxygen can be increased when smaller particles were used, which also improved the flow distribution. The increase of the cross sectional area ratio of central channel and outer channel was beneficial to flow distribution. The radial non-uniformity of velocity reduced with the decrease of the perforated-plate opening ratio of the central channel and outer channel, and the influence of perforated-plate opening ratio of central channel was more significant than that of the outer channel.