Abstract: Betulin extracted from bark of birch (Betula platyphylla Suk.) was purified by several kinds of mix-solvents. Purification effects and structure of betulin were analyzed by UV and FT-IR spectra respectively. Quantitative analysis of betulin was performed by HPLC. Yield of crude betulin extracted from bark of birch was 34.52% by weight. The most excellent mix-solvent was tetrahydrofuran-benzene. At the ratio of tetrahydrofuran to benzene 1:2 by volume, and ratio of betulin to mix-solvent was 1:30 (g:mL), yield of purified betulin was 31.19%, with a purity of 94.53%. Melting point of purified betulin was 248.9-251.3℃ and IR analysis conformed to literatures of the standard betulin sample. Comparing with the methods applied in the past, tetrahydrofuran-benzene extration is a simple and high efficient method to separate and purify betulin from birch bark.