In this study,larch wood,the main timber species in Northeast China,was improved by vacuum heat treatment to explore its cellulose morphology and structural thermal response mechanism. The wet chemical method was used to extract the cellulose of untreated and heat-treated larch wood under different vacuum heat treatment conditions (180~220 ℃,6 hours). The cellulose morphology was observed by scanning electron microscope,and its chemical structure and crystallinity were analyzed by X-ray photoelectron spectroscopy and X-ray diffraction. The results showed that the cellulose extracted from untreated wood was rod-shaped and had an ordered parallel and rigid structure. After heat treatment,the wood cellulose curved,and its surface twisted. With the increase inheat treatment temperature,the surface distortion of cellulose became more significant. The X-ray photoelectron spectroscopy analysis showed that the increase in heat treatment intensity decreased the cellulose O/C ratio from 65.5% to 59.5%. The C1 content increased,and C2 and C3 decreased,respectively,indicating that the cellulose carbon chain extracted from heat-treated wood was shortened. Hemicellulose and lignin-carbohydrate formed by the condensation reaction of lignin and carbohydrate during heat treatment might remain on its surface. In addition,with the increase inheat treatment temperature,wood celluloses crystallinity increased,the proportion of cellulose Ⅱ increased,and cellulose Ⅰ decreased. Furthermore,the morphology of cellulose extracted from wood before and after heat treatment presented different structures due to the differences in the cell structure and molecular group conformation between cellulose Ⅰ and Ⅱ. This research will help to deeply understand the thermal response characteristics of wood chemical composition and provide a theoretical basis for the optimization of wood vacuum heat treatment technology.