Abstract: The specific heat capacities of chars during primary pyrolysis of biomass with different conversion and the heat capacities of virgin biomass were determined. The ratio method was employed to measure the specific heat capacities of two biomass samples and their pyrolyzed chars through thermogravimetry and differential scanning calorimetry (TG-DSC). A mathematical model was developed to calculate values of specific heat of chars. The results show that the specific heat capacities of the two biomass samples and their derived chars increase linearly within 60~200℃. The values of the specific heat capacity of the chars are lower than those of the virgin biomass samples. The specific heat of chars decreases as the extent of pyrolysis increases. The calculated specific heat capacities from the developed mathematical model are quite close to those measured by TG-DSC analyses between 150~200℃.