In this study, we tried to understand the horizontal bearing performances of step-tapered piles using numerical simulations. The influence of the geometric parameters, e.g. the diameter ( D) and the distance (L), and the length ( H) of the pile were considered, and the soil distribution imposed on the horizontal bearing capacity of the piles was simulated. Numerical results show that when the other geometrical parameters of step-tapered piles are kept unchanged: (a) the increasing diameter ( D) of the enlarged upper part of step-tapered piles improves the horizontal ultimate bearing capacity of step-tapered piles; (b) reduced distance ( L) improves the horizontal ultimate bearing capacity of the step-tapered piles; (c) Increasing length ( H) of the enlarged upper part of steptapered piles increases the horizontal ultimate bearing capacity; (d) the reduced length ( H) decreases the bending moment of the pile body. Higher soil strength surrounding the enlarged upper part of step-tapered piles can increase the horizontal ultimate bearing capacity of step-tapered piles. The change of soil strengths at the end of the step-tapered piles does not influence the horizontal ultimate bearing capacity of step-tapered piles.