Based on the concrete damaged plasticity model, a CRTS Ⅰ track slab’s damage distribution model was established. The rail supporting force measured by Tekscan sensor was taken as load data, and the vertical displacement of track slab and the tensile damage factors were taken as calculating indicators. The inner damage law of the upper surface of track slabs near anchor pockets was analyzed when the debonding was between cement and emulsified asphalt (CA) mortar and track slabs existed in the passenger-freight line. Results showed that the critical heights of debonding for both initial damage and complete damage gradually decreased with the extension of the debonding length. When the debonding reached to the second and third anchor pockets, the critical heights of initial damage generated by the load under passenger car were about 0.8 mm and 1.0 mm, respectively; meanwhile, the critical heights under freight car were about 0.5 mm and 0.8 mm, respectively. Once the height of the debonding was greater than the critical height of initial damage, due to the development of the damage of track slab, the overall bending stiffness of the track structure decreased rapidly, resulting in a rapid increase of the vertical displacement of the slab end. Under the load of passenger car, after the debonding reached to the third anchor pocket and the height of the debondong was more than 1.0 mm, the CA mortar was formed into a void, and the displacement of the slab end did not increase any more. Under the load of freight car, when the debonding reached to the third anchor pocket and the height of the debonding was more than 1.3 mm, the vertical displacement of the slab end increased rapidly with the increase of the height of the debonding, due to the generation of the secondary damage zone.