Abstract: In consideration of degassing demands of produced fluids with relatively low gas content in offshore oil production, this work proposed a passive axial swirling degassing device. Based on this, the principle prototype was designed, and the degassing characteristic test was carried out in the self-circulating flow system. The test focused on the gas phase distribution inside the equipment, and it investigated the relationship among the split ratio, degassing ratio, gas content of the liquid after treatment, and the pressure drop. Studies have shown that by adjusting the split ratio reasonably, this device can reduce the liquid gas content to 0.1%. At the same time, there is a linear relationship between the inlet-overflow port relative pressure drop and the split ratio. The research results help to further reduce the space and weight demand of the tubular separation system.