After studying the variation law of the secondary wave transmission coefficient behind the breakwater by the physical model test of the sloping breakwater，this study establishes the relationships of the relative outlet height?Hc/Hs?and the relative levee top width?B/Hs?with the wave height transmission coefficient，and fit the nonlinear regression formula.At the same time，the fitting formula in this paper and the empirical formula are applied to calculate the height of the secondary wave behind the breakwater under different working conditions，and the results are compared with the test results.The results show that the proposed fitting formula is the most consistent with the experimental results and has good applicability.Then，the differences in the calculation results of other empirical formulas are analyzed.The results can provide a reference for engineering practice and the calculation of the post-dike secondary wave generated by the allowable surge at the top of the sloping breakwater.