Abstract: Wave transmission coefficient over a submerged breakwater is the main index to measure the wave weakened capacity of the submerged breakwater. A numerical wave flume is established by the MIKE21-BW model based on Boussinesq-type equations, and a numerical simulation of the regular wave transmission coefficient over the submerged breakwater is made in this article. According to the results of Dingemans physical model tests, the parameter calibration and verification of the BW model are carried out, and the results are satisfactory. On the basis of these results, further analyses of the dimensionless parameters influncing the submerged breakwater wave transmission coefficient, including relative submerged water depth, wave steepness, relative crest width of the submerged breakwater, submerged breakwater slope, are made. And the change law of different combined factors of the submerged breakwater wave transmission coefficient is studied. The form of a calculation formula for the regular wave transmission coefficient over the submerged breakwater is put forward, and MATLAB mathematical software is used to fit the coefficient of the formula. The correlation coefficient between the calculated value of the fitting formula and the calculated value of the BW model is 0.858, a good correlation between the two values. In addition, the difference and relevant reasons of the data between the fitting formula and Yang Zhengji's formula are compared and analyzed. The analysis results show that the MIKE21-BW model can be applied to the numerical simulation of the submerged breakwater wave transmission coefficient under the action of the regular wave. The results given by this article can provide a reference for the numerical simulation of the submerged breakwater works.