For the 2-D system of wave motion, consider a free surface progressive gravity wave train propagating over a random ripple seabed and there will be an interaction between surface wave and seabed. By spectrum analysis, getting the components of ripple seabed to make a Fourier form and a perturbation expansion procedure will be developed to second order to solve the flow field. Because the different type of spectrum will make different ripple seabed, the affect made by components of ripple seabed will change with the type and it¡¦s bandwidth, and the resoults predicted in model of this paper can become systematic .It is helpful for design of engineer.