Abstract: In order to study the variation of the type and content of free amino acid in different soil layer, as well as the influence of different forest types on free amino acid content in the boreal forest of Greater Hinggan Mountains, a reverse-phase high performance liquid chromatographic method for simultaneous determination of 17 free amino acids in soil with gradient elution technique at 254 nm UV wavelengths was applied. It can not only determinate the concentration of the total amino acid content, but also the content of each amino acid component accurately. Furthermore, it has better derivative effect and high separation efficiency. The results showed that the average contents of free amino acids in the different forest were Rhododendron-Betula platyphylla forest(33.86 μg/g)>Rhododendron-Larix dahurica forest(31.44 μg/g)>Ledum palustre-Larix dahurica(28.76 μg/g)>Pinus pumila forest(27.66 μg/g). In the same forest, the size order of free amino acid nitrogen content of every soil layer was litter layer> mineral layer, and the 0-5 cm of mineral layer> the ≥5-20 cm of mineral layer. There is some difference of the types as well as the content of free amino acid in different forest types of soil layer, and the type of free amino acid was the most in litter layer. Neutral amino acid content was the highest, followed by alkaline and acidic amino acid, and sulfur-containing amino acid was lowest. This studie showed that different forest types have generated various effects on the content and type of soil free amino acid accounting for various stand climatic environment, edaphic conditions, and understory associated trees.