The three-dimensional wave physical modeling has been widely employed in the breakwater design. Compared with the conventional 2D wave physical model，the 3D model has the merits in full description of the wave-structure interaction. The 3D random wave integral physical model test can quantify the wave shoaling，refraction and diffraction，overtopping amount and 3D stability of coastal structures. Taking the breakwater project of port in Trà Vinh，Vietnam as an example，a 1：34.3 3D integral wave physical model is used to test and study the 3D stability of the breakwater head and body and overtopping amount of breakwater under different wave directions and return periods. The test results show that：1） The breakwater is reliable and stable when the head of the breakwater is 5 t and the trunk is 3.5 t. 2） Only a small amount of overtopping or splashing occurs at the extreme high water level and design high water level.