Objective:To study the content changes of Saikosaponin a

b1

b2

h in the process of the preparation of Saiko decoction. Method: A HPLC method was employed

which was carried out on a Hypersial C18 column (4.6 mm×250 mm

5 μm) with gradient elution of acetonitrile-water (0-70 min

28∶78-50∶50). The flow rate was set at 1.0 mL·min-1. The column temperature was 30 ℃. The wavelength was set at 210 and 254 nm. Result: The contents of saikosaponins vary greatly with the time of decoction. The content of saikosaponin a

which decreased with the decoction time

tended to be stable after 4 hours. However the content of saikosaponin b1

b2

h increased with the decoction time. The content of saikosaponin b1 was also in the ascent stage after 5 hours. The saikosaponin b2 reached its stability stage after 2 hours. And the saikosaponin h tended to be stable after 4 hours. Conclusion: Attention should be paid to the influence of decoction process when research was carried out on the chemical constitution compatible regularity of saiko. This paper set foundation to the research model of compatible regularity for the Chinese crude medicines containing unstable chemical constitutions.