Nonlinear soil-structure interaction effects under strong ground motions should be considered in the seismic design. This paper presents the results of cyclic loading test for pile foundation in dry sand to investigate the nonlinear behavior of pile foundation in large displacement range. The experimental parameters are the number of piles, loading rate, relative density of soil and alignment of pile group. The major findings obtained from tests are summarized as follows: l) the soil around piles deformed significantly even at small amplitude, 2) shear force-displacement relationship, resultantly secant stiffness and equivalent damping factor, at pile head shows significant nonlinearity even in very small displacement range, 3) shear force at pile head hold almost constant value after the soil get failed.