Abstract: Based on the forest fire data in Daxing'an Mountains of Inner Mongolia from 1981 to 2020, the temporal variation characteristics of 3 fire sources were analyzed; trend analysis by MK mutation test; the spatial distribution patterns of 3 fire sources were analyzed by multi-distance spatial cluster analysis and kernel density analysis. The results showed the radiation range of lightning fire in Daxing'an Mountains of Inner Mongolia from 1981 to 2020 is the widest, and smoking fire and agricultural fire are relatively concentrated. The occurrence frequency and harm of 3 kinds of fire sources(except lightning fire frequency is increasing) are decreasing. Lightning fires occur frequently in summer, most active in May, June and July, and most frequently in 00: 00–0: 59, and most harmful in 04: 00–4: 59. Smoking fires and agricultural fires occur frequently in spring, most active in April and May, and most frequently in 08: 00–19: 59. The key prevention areas of lightning fire are the northern original forest area, Mangui, Alongshan, Moerdaoga, Genhe, Ganhe, Keyihe and Yitulihe Forestry Bureau. The key prevention areas of smoking fire and agricultural fire are Dayangshu and Bilahe Forestry Bureau.With the gradual strengthening of fire source control, forest fire monitoring and extinguishing capacity in Daxing'an Mountains of Inner Mongolia, the total area of fire caused by the 3 fire sources in recent years has decreased significantly compared with the previous. Forest fires caused by the three fire sources mostly occurred in spring and summer. The forest fires caused by the 3 fire sources were significantly clustered in space.