A two-dimensional forward simulation was conducted to analyze slab ballastless track diseases in high-speed railway using the ground penetrating radar (GPR) technique. Based on the finite difference method, a two-dimensional forward simulation equation for GPR was deduced. By considering the different filling degrees and hardening progress of CA mortar layer, GPR geoelectric models for CRTSⅡ slab ballastless track were established and forward simulated, and the GPR picture features of the forward simulation were analyzed. The simulation results show that the forward simulation can clearly identify the interfaces between different dieletric layers and the number and location of reinforcement in slab ballastless track.