This study utilizes a 3D DEM sleeper-ballast bed model, comprising four sleepers interacting with the actual shape of the ballast, to comprehensively explore the impact of sleeper-ballast interaction and ballast aggregate friction coefficient on the lateral resistance of ballast bed. Based on the DEM numerical simulation, the following conclusion can be drawn: 1) The friction resistance between the sleeper and the ballast is crucial in determining the lateral resistance in railway tracks, with the base ballast contributing to more than 50% of the lateral resistance of the ballast bed on average; 2) The sleeper bottom resistance and sleeper side resistance of lateral force is derived from the sleeper-ballast friction mechanisms, while the friction coefficient between the sleeper end and the shoulder ballast has minimal impact on the sleeper end resistance; 3) The lateral resistance of the ballast bed is more significantly influenced by alterations in the ballast friction coefficient than by changes in the friction coefficient sleeper-ballast interface.