Abstract: The bearing capacity of X-section cast-in-place concrete pile (XCC pile), a special cross-section pile, is significantly influenced by side resistance. The single-piled composite foundation including XCC pile and circular pile is simulated by means of the finite element program ABAQUS. The side resistance and side bearing capacity are compared between XCC pile and circular pile. The distribution of side resistance of XCC pile is analyzed via cross-section plan and depth. The results indicate that both the side resistance and the side bearing capacity for XCC pile are better than those of circular pile, and that the side bearing capacity of XCC pile is significantly larger than that of circular pile at the relative depth of 0.9. At the cross-section plan, because of the soil arching, the side resistance of convex arc is about 1.5 to 3 times as large as that of concave arc for XCC pile. The ratio of the side resistance for convex arc to that of concave arc increases with the relative depth. The results are available for the design of XCC pile.