When p-y curve is applied to mechanical analysis of group piles, the pile-top displacement is not sum of displacements induced by force and moment. Therefore, the finite difference method is firstly employed to get modulus of foundation support of each point. The stiffness coefficient of each pile-head is then determined by the transfer matrix. Finally, the iterative circulation calculation is processed by p-y curve method based on the above two steps. It is shown that the results obtained by the method mentioned in this paper agree with those by finite difference method. In addition, by comparing with the method mentioned, the displacement and the internal force obtained by the “m” method is not safe.