Objective: To optimize the Saussurea involucrate sustained-release tablets and to study the release mechanism of the mainactive composition of Saussurea involucrate. Method: The amount of HPMC and MCC

the ratio of starch with lactose were screened by using method of orthogonal design and by selecting cumulative release of chlorogenic acid and rutin as index. Mathematic models were used to imitate the drug release. Result: The optimum formula was as follows the amount of HPMC K15m was 17%

the ratio of starch with lactose was 2 ∶1 and the amount of MCC was 1%. The release of chlorogenic acid and rutin was conformed to Higuchi equation. Conclusion: The release of two mainactive composition of Saussurea involucrate could be well described in vitro and give good foundation for rationality of formula design.