Denitrification and its products (N2, N2O and NO) in four forest soils collected from Changbai Mountain were investigated by acetylene inhibition method applied to a laboratory incubation under flooded condition with N2 gas in the headspace. The tested four forest soils are all acid, soil pH varied from 4.5 to 5.0 and the organic carbon changed in 24.6-83.0g kg-1. The results showed denitrification potential and composition of denitrification products varied greatly among the investigated soils with a decreasing order of denitrification potential: Pinus koraiensis > Betula platyphylla Suk.> Pinus koraiensis - Picea asperata (Mast.) - Akjes fabri (Mast.) > Larix gmelini（Rupr.）. Denitrification potential was positively correlated with soil organic carbon and nitrogen content significantly (p<0.01), not significantly with soil pH. Compared the Treatments with acetylene inhibition and no acetylene inhibition, we found that during the period of incubation, N2O was always the dominant product of denitrification, accounting for 50% ~ 85% of total N gas production. The ratio of N2O to total N gas production was weakly correlated with soil pH (p = 0.12). NO was a minor product of denitrification, accounted for only 0.2% ~ 2.4% of total N gas production. A significant logarithm correlation between the ratio of NO to total N gas production and the soil organic carbon content was observed to be significant (p<0.05). These results implied that denitrification process would not transform reactive nitrogen into inert nitrogen (N2) effectively in Changbai Mountain forest soils and the significance of the denitrification removing reactive nitrogen should be re-assessed.