Abstract: Finite element model of high-speed railway bridge and CRTS II slab ballastless track structure is established.Track irregularity under different pier top displacement calculation working conditions is calculated and analyzed, and the displacement limit value of fixed bridge substructure is recommended considering relevant specifications. It is found that pier lateral displacement has a larger impact on track irregularity, and the extreme value of the track irregularity is basically in a linear relationship with the pier lateral displacement, and the limit value of pier lateral displacement is recommended to be 9 mm. Pier vertical displacement has larger impact on height irregularity. The extreme value of height irregularity is basically in a linear relationship with pier vertical displacement, and the limit value of pier vertical displacement is suggested to be 12 mm. When a two-way displacement of the pier occurs, both the height and track irregularity will be slightly increased, thus the limit value of pier two-way displacement is recommended to be 7.2 mm.