Abstract: For the equipment or processing which consumes a greater amount of heat, heat balance determination should be made to get better understanding of the distribution of energy consumption so that ways of saving energy can be explored. This article gives a systematic account of how heat balance determinations are made in two types of lumber drying, and suggests a calculation method for comparing heat efficiency in different kinds of kiln drying. Based on the data collected at the Shanghai Fiberboard Factory, the article discusses the rationality of the present technology and equipment of kiln drying from the angle of its utilization ratio of energy. The data concerning the results of determinations and calculations from this factory show that for the present lumber kiln drying there is great potentiality in saving energy. In addition to the improvement of the steam and heat supply system of the kiln, the author suggests that the use of steaming should be restricted or even replaced by some other means, and also that effective methods to control the exhaust-gas from kilns should be introduced. In order to ensure the effectiveness of the technology mentioned above, it is imperative to make sure of the air-tightness of the kiln. For the sake of energy saving, it would be worthwhile to increase the investment in building a new kiln.