To study the chemical constituents in Cassia Bark. Methods:Silica gel, ODS, Sephadex LH-20 column chromatography and semi-preparative HPLC were used to isolate and purify the compounds of Cassia Bark. The structures of the compounds were identified on the basis of their physicochemical properties, spectroscopic data, and with the literature. Results:Seven compounds were isolated from the Cassia Bark including (-)-secoisolariciresinol (1), (-)-isolariciresinol (2), Erythro-1-C-syringylglycerol (3), (-)-gynuraone (4), zhebeiresinol (5), coniferyl aldehyde (6), cinnamic acid (7). Conclusion:Compounds 1~3 were isolated from Cassia Bark for the first time. Compounds 4~5 were obtained from this genus plants for the first time.