将多重尺度法的导数展开法引入Ｎ－Ｓ方程的尺度离散，对各阶近似中变量采用Ｒｅｙｎｏｌｄｓ分解，并根据多重尺度的可解性条件，得到不同尺度的潮流、波浪方程用数学方法解释了潮流波浪的相互作用和影响，并与Ｒｅｙｎｏｌｄｓ方程进行了比较 The method of derivative expansion of multi-scale method is introduced to measure the discreteness of N-S equation. Reynolds decomposition is applied to the approximate middle variables of each scale. According to the solvability conditions of multiple scales, the power flow of different scales is obtained. The wave equation is explained mathematically The interaction and influence of tidal waves are compared with the Reynolds equation