The influence of the different airway structure on mixing time of molten steel are studied through using water model experiments. The bubble volume and velocity have been investigated through the PIV for different airway structure in the flow of 1m3/h. Results showed that with the slit distribution same, the smaller the slit width, the greater the volume percentage of the large bubbles and the average velocity of the bubbles in rising, but the shorter the mixing time. Reduce the number of the slit can lead to the volume percentage of the large bubbles and the average velocity of the bubbles in rising decreases, the mixing time extended, and it is more obvious to the mixing time to reduce the number of the inner slit. Inflatable volume<1.1m3/h, with the slit in the outer ring only and the number of slit same, the volume percentage and the average velocity of the large bubbles in rising is larger, the mixing time is reduced. Inflatable volume≥1.1m3/h, the slit evenly distribution is better for mixing.