In order to explore the reaction heat of biomass pyrolysis process, and establish the energy balance relationship of the pyrolysis reaction, the pyrolysis reaction of the spiral reactor and the pyrolysis experiment using the thermal differential thermogravimetric were carried out. The spiral reactor pyrolysis experiments were carried out by using four different temperatures of 500℃, 550℃, 600℃, and 650℃, and two different residence times of 5 min and 10 min, respectively. According to an electric meter, the pyrolysis power consumption of the spiral reator was recorded. Then the heat of pyrolysis reaction is calculated by the electrothermal conversion efficiency of the reactor. Thermogravimetric pyrolysis experiment measures the reaction heat by integrating the DSC curve. In addition, the reaction heat of the pyrolysis process was also calculated by fitting formula and other theoretical methods. The result shows that the reaction heat measured by the electric meter is approximately 1 MJ/kg, while the reaction heat measured by DSC curve integration is 0.6-0.8 MJ/kg. The results calculated by the fitting formula deviate greatly from the experimental results. This experiment provides a valuable reference for optimizing the calculation and measurement of reaction heat in biomass pyrolysis process.