Abstract: Based on Reynolds transport equation，stress tensor expression ρvi vj of momentum flow was derived． The curved surface integral was calculated along the surface of entire controlling body ( sitting mark do，get the surface integral) and a joint effort， namely radiation momentum stress was attained． The results through the method was adopted to calculate decrease water equation． Compared with traditional reducing water equation，the analysis show that radiation momentum stress not only embodies the essential characteristics of“radiation stress”，but also expands the application scope of radiation stress．

Key words: waves, radiation momentum stress, analysis, decrease of the surface of waves

摘要： 从雷诺输运方程出发，推出动量流的应力张量表达式ρvi vj，沿整个控制体的外表面做曲面积分( 对坐标的曲 面积分) ，得到的是一个合力，称为“辐射动量应力”。并将这种新计算方法求得的结果应用于求解波浪减水方程， 与传统减水方程比较后得出: “辐射动量应力”不仅体现了“辐射应力”的本质特征，还拓展了辐射应力的适应 范围。

关键词: 波浪, 辐射动量应力, 分析, 波浪减水现象