Composite ground can be regarded as transversely isotropic material. Semi-analytical element method is used to study the dynamic interaction of slab and composite foundation. It can avoid introducing redundant boundary condition compared with FEM

and improve computation accuracy. Furthermore it can simplify 3-dimensional computation to one dimension

saving computation time dramatically for its quick convergence. The dynamic property of slab and composite ground is investigated by means of changing substitution ratio

reinforced depth and modulus ratio of pile to soil. The results indicate that the increment of these factors can affect the amplitude of vibration and increase the system's frequency. So when designing the foundation of power machine

some attention should be paid to the impaction of composite ground on the alteration of dynamic property of ground.