Abstract: Offshore wind turbines are mainly located in shallow water, and the nonlinear characteristics of the wave forces are quite significant. The stream function wave theory which can simulate arbitrary order nonlinear wave is of general applicability. The stress and deformation of pile foundation of wind turbines are analyzed on the basis of the function wave theory in combination with the Morison equation and the p-ycurve under reversed cyclic load. According to an engineering practice, based on the stream function theory, using the non-dimensional method, the velocity, acceleration and wave surface distribution of three water depths are compared firstly, and then distribution differences of wave force and wave moment are calculated. Finally, the differences of inner force and deformation of piles are investigated. The results indicate that variations of wave parameters will result in significant changes of internal forces and deformation of the piles. Therefore, the foundation design of offshore wind turbines needs accurate wave parameters. A database for wave parameters which facilitates the estimation of wave force in the initial designs is suggested.