Abstract: To study the damage change law of ballast slab under complex conditions, through the approach of concrete plastic damage model, by applying temperature load on it and obtaining the external excitation from the metro vehicle-track coupling dynamics analysis, a train-track-subgrade coupling model is established and analyzed. The results show that when the temperature decreases, the ballast slab will produce transverse deformation and internal cracks appearance, leading to damage, stiffness decrease, concrete material softening, and the decrease of structural tensile bearing capacity. But in the subsequent temperature rise process, the damage of ballast slab remains unchanged, and is finally stabilized at about 0.19. When the train load is applied to the damaged ballast slab, the internal crack will close and the rigidity restores temporarily. However, due to the periodic opening and closing, the crack of the concrete ballast slab will develop rapidly and finally forms the penetrating crack.