【Objective】To reveal the change trend of combustibility of burned area combustibility and its influencing factors in lightning burned areas, so as to provide theoretical support for fire risk assessment of lightning burned areas in the Daxing’an Mountains in China.【Method】Using the method of "space-time displacement", the combustibilities on the forest surface fuel of Larix gmelinii with different times after fire in the Tahe area of the Daxing’an Mountains were taken as the research object to determine their physical and chemical properties.【Result】The litter layer of the forest surface fuel was more flammable at 17-23 after fire, and the ash content had the greatest impact on its flammability. The biomass of other tree species, time after fire and slope aspect significantly affected the comprehensive flammability (P< 0.05). The calorific value of surface fuel in the fermentative layer has the greatest influence on its flammability. Terrain factors had no significant effect on the flammability of forest surface fuel in the fermentative layer (P > 0.05). Ash content, calorific value and fat significantly affected the combustibility of forest surface fuel (P < 0.01). Ash content and high calorific value are the most important factors affecting the combustibility of forest surface fuel in litter layer and fermentative layer, respectively.【Conclusion】The forest surface fuel in the litter layer 17-23 years after the fire and the fermentative layer 11-23 years after the fire are more flammable. Ash content, calorific value, fat and hemicellulose are significant factors affecting the combustibility of forest surface fuel. The time after fire, biomass of other tree species, slope aspect and slope position significantly affected the flammability of forest surface fuel in the litter layer. The effects of time after fire, biomass and terrain factors on the flammability of the fermentative layer were not significant. Therefore, we should focus on the control of lightning fires that have been burned for 11-23 years.