Heat treatment is a green, environmentally friendly and mild pyrolysis process that improves the dimensional stability and durability of wood. in this study, Larix spp. Samples were heated at 180 °C and 210 °C for 6 h with nitrogen, air or oil as heat-conducting media. The influence of high-temperature heat treatment on the microstructure, chemical components, and micromechanical properties was investigated. the mass loss rate increased with increasing temperature, and the degradation of wood components resulted in cracks in the cell walls. Samples treated with air showed more cracks in cell walls than were observed in the cells walls of wood treated with the other heat-conducting media. the hardness of the cell walls increased after all heat treatments. in addition, the results showed that heat treatment reduced creep behavior compared to that of untreated wood.Larix spp., an appealing source of wood products in China, are massively planted due to their excellent adaptability, rapid growth and long growth cycle. However, the poor dimensional stability and durability of these species severely limits their scope of applications 1 . Recently, several industrial-scale and environmentally friendly heat treatment processes were applied to solve these problems without the addition of chemical agents, including Retification ® , Thermowood ® , Plato Wood ® , OHT ® and so on 2 . The equilibrium moisture content (EMC) and hygroscopicity of wood decreased markedly after heat treatment, which could prevent several appearance defects, such as blue staining and white rot. Moreover, after appropriate heat treatment, wood durability can be enhanced significantly, which extends the life cycle of the wood products accordingly 3 .Heat treatment, a green process, alters the chemical composition of wood through pyrolysis of the hemicellulose and part of the amorphous cellulose, evaporation of extractives and condensation of byproducts 4,5 . This procedure caused a higher degree of cellulose crystallinity, lower hydrophilicity, improved color, and better dimensional stability and durability of wood 6,7 . The mechanical properties of heat-treated wood, including compression strength, modulus of elasticity, modulus of rupture, brittleness, impact bending and so on, have been extensively reported on 8 . Previous studies have shown that the elemental composition (C/O ratio or C content) is a useful marker for predicting the level or extent of heat treatment 9,10 . These markers can also be effectively used for the prediction of decay durability and mechanical properties of heat-treated wood. Furthermore, the mass loss rate is also a notable feature in heat treatment and is a parameter used for quality control 11,12 . It has been massively proven that chemical transformations of compounds and extractives in wood cell walls is caused by heat treatment 13,14 . These transformations are mainly dependent on the wood species, treatment duration, heat temperature and so on 15-17 .If wood heat treatment involves air on an industrial scale, a lowe...