Abstract: In this paper, we have researched the changes of swamp soil after the great fire event occurred on 6 May, 1987 in the Da Hinggan Mountain. It is revealed that the fire had severely effected the soil profile by burning away the organic matter in topsoil. Soil thermal situation has been changed, and soil temperature rise. Soil water content has been altered because the water reservation condition has been changed by the fire. Soil pH and the content of P₂O₅, K₂O, CaO, MgO increase after the fire, on the contrary, the organic matter content and N content decrease, the quantity of microorganism greatly increased after the fire. It is considered that the fire is beneficial to the development and genesis of swamp soil in this area.