The paper is to report the observation of pharmacokinetic changes of the characteristic ingredients in the combinations of different-dose herbs of Shaoyao-Gancao decoction.  After the establishment of HPLC analytical method of plasma effective constituents, rats were orally administered with different-dose herbs of Shaoyao-Gancao decoction.  Blood samples at different times after administering these decoctions were collected, and then were analyzed by HPLC fingerprints technology.  Pharmacokinetic parameters of characteristic peaks were analyzed by SPSS 15.0 software and DAS 2.0.  At last, we looked for the correlation of those pharmacokinetic parameters and the dosage of Gancao.  The best dose of Shaoyao-Gancao decoction was at the ratio of 4 to 4, which was consistent with the dose commonly used in ancient times.  The absorption of characteristic peaks from Shaoyao-Gancao decoction was related with the dosage of Gancao, and there existed interaction between each characteristic ingredients.  There existed the right dose-ratio of Shaoyao and Gancao to get the best effect.  The absorptions of effective constitutents were mutual waxing and waning in order to increase biological effects together.  It’s demonstrated the compatibility connotation at a right dose-ratio of Shaoyao-Gancao decoction through the angle of pharmacokinetics.