A concrete is a porous structure and its internal temperature response is different from those of metal materials, a sudden temperature change at the initial stage is found experimentally, this phenomenon cannot be described by a differential model. A fractal heat conduction model is established to reveal the effect of the concrete’s porosity on the internal temperature response. The method of separation of variables for fractal differential equations is adopted to solve the problem, and the theoretical result is compared with the experimental data, showing a good agreement.