To investigate the lateral ultimate bearing capacity of cantilever rigid piles subjected to large horizontal displacement, this paper analyzes the distribution characteristics of soil resistance along the pile side and explores calculation methods for lateral bearing capacity of pile foundations using both numerical simulation and theoretical approaches. The results indicate that, under large displacement conditions, the soil in front of the pile yields progressively from top to bottom. Once the soil adjacent to the pile reaches its limit displacement, the lateral soil resistance no longer increases with further displacement. The ultimate lateral bearing capacity of cantilever rigid piles under large horizontal displacement is determined based on the ultimate displacement of the side soil. Among the tested approaches, the modified “m” method demonstrates the best fitting accuracy. However, further investigation is required to define the applicable range of foundation coefficient distribution.