Abstract: he study shows:1.Soil microorganisms are mainly concentrated in upper layer. Their amount decreases with increasing soil depth.2.The amount of bacteria is very rich in rainy season and counts for more than 95%of the total.With the coming of dry season, the amount of bacteria decreases,and that of actinomycete and fungi increases.3. The amount of microorganisms, the intensity of cellulose-decomposition, the activity of soil enzymes and the intensity of soil respira-tion are decreased in order of: 20-years-old secondary forest>12-years-old secondary forest> 7-years-old secondary forest.

Key words: acid rain region, forest health, water deficit stress, Masson pine forest.