Abstract: The composition and distribution of the soil microflora,the intensity of soil respiration,and the activity of soil enzymes under three different forest types on the Northern slope of the Changbai Shan Mountain Natural Reserve in three diffrent seasons (Spring,Summer and Autumn) in 1982 were studied.The results indicated that under diffrent types of forest,the ecological distribution of soil microorganisms,the intensity of soil respiration and the activity of soil enzymes in three seasons were diffrent.But the tendency of variation was higher in Spring,lower in Summer and increased in Autumn.The number of soil microorganisms,especially the number of soil bacteria,and the intensity of soil respiration under broad-leaved and coniferous mixed forest was greater than that under the coniferous forest.