The purpose of this study is to clarify the loading rate dependency of subgrade reaction for a single pile in liquefied ground. The parametric studies were performed by incorporating the dynamic soil-pore water coupled formulation and a newly proposed constitutive model. The model can explicitly treat the degree of liquefaction by changing the lower limit of the mean effective stress. The liquefied soil at a certain depth around a pile is modeled with finite elements under the plane stress condition. The subgrade reaction for a pile is calculated under various loading frequencies and degrees of liquefaction. The results of the parametric studies show that the correlation in p-y (subgrade reaction-pile displacement) relations and p-v (subgrade reaction-pile velocity) relations depends on the loading frequency and the degree of liquefaction. The numerical method can reproduce the loading rate dependency of the subgrade reaction for a single pile without the viscosity constitutive model and numerical damping.