In order to accurately reflect the influence of external environmental factors and concrete properties on the temperature change in CRTSⅡ track slab of a line in eastern China, considering the time delay of heat flow at different depths caused by hot pressing, the relationship between temperature at different depths of track slab is studied by using the spectrum method. Referring to the thermodynamic theory, the calculation model of temperature at different depths of track slab concrete is established, and the sunshine real-time temperature field and vertical temperature gradient of track slab in this region are studied. The results show that the delay time of heat flow caused by temperature gradient is proportional to the propagation distance in the same medium. The temperature series at different depths of the track slab are relative to the surface layer, and the amplitude decays with an exponential function, and the slab has a linear lag. During the heat transfer process in the track slab, the track slab temperature change delay time is about 1.02 h with each depth of 50 mm. The average relative error of the temperature calculation model based on the heat flow delay track slab is between 1.9% and 2.5%, and the reliability is between 92.85% and 96.53%.