Most piles are set in layered soils. The initial foundation coefficient, a hyperbolic p-y curve containing a parameter, is derived to generally simulate the nonlinear soil around the pile. The soil around the tested pile is nonlinear, and both the tested and the calculated lateral displacement of the tested pile at the ground have a parabolic relation with the horizontal loads. The calculated lateral displacements of the tested pile at the ground fit the tested lateral displacements very well, and the hyperbolic p-y curve is proved good. The nonlinear soil will greatly increase both the maximum moment of the pile and the soil pressure. Thus it is suggested that the designed moment of the pile which is calculated by m-method, should magnified 1.05~1.25 times in order to consider the nonlinearity of the soil around the pile.