Abstract: An experiment of the dissolved oxygen transport and diffusion with water and air mixture in plug discharge is established, in order to study the undersaturated dissolved oxygen behavior of water and air mixture plug discharge and illustrate the influence of air volume fraction, inlet dissolved oxygen concentration, Reynolds number and geometry size on dissolved oxygen concentration. Velocity, pressure and dissolved oxygen concentration are measured, respectively. A three-dimensional mathematical model of dissolved oxygen transport and diffusion is established to compute water and air mixture flow, and, it is validated by the experimental data. It is used to compute the dissolved oxygen distribution with different inlet air volume fraction, dissolved oxygen concentration, Reynolds number, length, and diameter of the plug section. The results show that the increment of dissolved oxygen concentration increases with increasing air volume fraction, and, increasing difference between inlet dissolved oxygen concentration and saturation dissolved oxygen concentration, respectively. It also increases with decreasing Reynolds number. Finally, it increases with increasing length of plug section, and increases with decreasing diameter of plug section.