Abstract: For higher accuracy in simulating the transformation of three-dimensional wave,applying the advantages of the constant panels and linear elements,a combined boundary element is applied in this research.The method can be used to get rid of the transverse vibration due to the accumulation of computing errors.A combined boundary condition between the Sponge layer and the Sommerfeld radiation condition is used to remove the reflected waves from the computing domain.By following the water particle on the water surface,the third order Stokes wave transform is simulated by the numerical wave flume technique.The computed results have good agreement with theoretical one.