Abstract: In recent decades, the small-scale pressure swing adsorption (PSA) oxygen generator has been widely used in the fields of home medical and hospital oxygen supply, anoxic environments, and plateau environments due to its cost effectiveness, operational flexibility, and adequate O₂ volume fraction. The flexible optimization of PSA oxygen generation in response to changes in product demand is an important factor in its practical performance. To study the influence of a variable product flow rate on O₂ volume fraction in the small-scale PSA oxygen generator, experimental equipment was set up, which consisted of a modified Skarstrom-cycle two-bed PSA system. The research results show that variations in the parameters at the lower product flow rate (≤10.37 L·min⁻¹) may have a negative effect on oxygen countercurrent mixing, which can impair oxygen generation, and at higher product flow rates (≥13.57 L·min⁻¹) may cause the negative effect of nitrogen breakthrough, which decreases the working capacity of the adsorbents in the bed. The O₂ volume fraction at the lower product flow rate was improved by increasing the ratio of total oxygen in the purge gas to the total oxygen in the feed gas (P/F) and by decreasing the ratio of the highest adsorption pressure to the lowest desorption pressure (θ) during a cycle to suppress oxygen countercurrent mixing. The O₂ volume fraction at the higher product flow rate was improved by increasing the P/F and θ values to improve the working capacity of the adsorbents in the bed. Accordingly, adjustments are made in the P/F and θ values at the lower and higher product flow rates to achieve optimal oxygen generation performances, enhancing the O₂ volume fraction from 92.4% and 74.0% to 95.7% and 74.9% at the respective product flow rates of 3.55 L·min⁻¹ and 19.88 L·min⁻¹. This work is meaningful for the optimization of the parameters of the PSA oxygen production process at variable product flow rates.