The oxygenation performance of the swirling aerator was evaluated by an air-water system oxygenation experiment. The flow pattern analysis on the oxygenation process of the swirling aerator was carried by PIV measurement and numerical simulation. The test results showed that the oxygen transfer coefficient (KLa) increased with the increase of intake air volume, and the maximum value of KLa (20°C) was 0.721L/min under 8m3/h condition. PIV measurement results showed that the number of tiny bubbles in the water increased with the increase of intake air volume and the bubbles form vortex in the pool with the water flow, which enhanced the mass transfer effect. The maximum number of tiny bubbles appeared at 8m3/h. The results of numerical simulation showed that due to the difference in speed, obvious vortex phenomenon occurs. With the increase of intake air volume, the intensity and quantity of vortex increase, the air-water mixing was more sufficient, and the air volume fraction was higher.So the oxygenation performance was stronger, which was consistent with the PIV measurement and oxygenation test results.