Abstract:In this paper, a comparative study on the contents of constituents—the active rhatannins, d-catechin and gallic acid in rhubarbs and its processed products is reported. The result shows that different processing methods have significant effect on rhatannin and its monomer, d-catechin and gallic acid. When the rhubarbs were stewed for 30 hours or boiled under pressure over 4 hours, the content of d-catechin in the processed products was greatly decreased or even disappeared, while the amount of gallic acid was increased. The result has certain significance for illustrating the pharmacodynamic change of the purgative and antibacterial action of processed rhubarbs.