A mathematical model was established by using the transfer matrix based on Winkler elastic subgrade and spring supports in Newmark method. In simplification for subgrade reaction with discrete spring supports, the unequal displacements of two ends for pile section were included in the model. Lateral displacement and cross-section angle of the pile were determined by lateral static load test and the values of parameters of multiple subgrade reaction models were calculated by computer programming. By identifying the stability of long pile in different subgrade reaction models, the change patterns of three factors were analyzed, including effective length of long pile, restrictions on pile top and extensive length on the ground.