Mathematical models for the thermal system of the modulated temperature differential scanning calorimeter were studied paying attention to the high frequency region. We took account of the thermal resistance between the pan and the base plate, deviation from the symmetric thermal system and time lag between the temperature of the base plate just below the pan and the measured temperature. Two types of equations for data analysis using only the temperature difference between the sample and reference sides are presented. The upper limit of the sample thickness for meaningful measurement was critically studied using thermal diffusion equation with proper boundary conditions. Results of the calculation were in good agreement with experimental results by the light heating modulated temperature differential scanning calorimetry (LMDSC).