The bearing capacity of large diameter piles in Dalian is simulated with FLAC3D software, and the bearing capacity of conventional piles and bell-out piles are compared and analyzed. The results show that the FLAC3D software simulated changes in Q-s curves fit the actual measured ones for conventional piles under the same load, indicating that the established FLAC3D model is suitable for study of those piles. The FLAC3D model is used to analyze stress of bell-out piles and conventional piles under the condition of 6000kN load and the same pile diameter. Under the condition of the same stress at the top of pile, the stress at the end of pile is reduced by 50%, and the stress condition at the end of pile is improved. Under the condition of the same pile length, the bearing capacity of the bell-out pile with reduced diameter is studied. The material used is 61.2% of the conventional pile. The simulation results show that the bell-out pile with reduced diameter can meet the engineering load requirements and reduce the cost. It is suggested that the original design should be revised to provide a theoretical basis for similar projects.