The scale parameters of bubbles produced by underwater exhaust influence the effect of the acoustic insulation. According to the dynamic characteristics in the process of underwater gas exhaust and the design criteria of equal flow per unit area， the two dimensional exhaust equation of underwater gas is established. The analytical expressions of the opening position and geometric parameters of the two dimensional exhaust device of underwater gas are obtained. The finite element models are established to compare the two vent patterns of uniform distribution and constant pitch/variable size distribution. The exhaust effect is verified by circulating flume test. The simulation and experimental results show that the distribution mode of fixed orifice spacing and variable orifice area can effectively control the distribution of bubbles scale parameters， and enhance the acoustic insulation effect of bubbles.