Variation of reaction heat of cedar wood pyrolysis with the variation of product distribution was estimated by means of heat balance calculation. For estimating the reaction heat of pyrolysis, heat balance was calculated with heating values of gas products, oil and char. Heating values of char and oil, except for gas product, were estimated with an estimation equation using only elemental composition of the products. The above heat balance indicated that the reaction heat of pyrolysis distributed in a wide range from -0.5 to 1.5 MJ/kg with the variation of product yields. The thermal decomposition of char and oil vapor to permanent gas during pyrolysis contributes to the endothermicity of reaction heat, while the production of the oil vapor from cedar pyrolysis contributes to the exothermicity of reaction heat. The gas composition also affects reaction heat distribution. Decrease in CO yield results in exothermicity of reaction heat. Increase in CH4 contributes to exothermicity of reaction heat. (C) 2016 Elsevier B.V. All rights reserved.