Objective: To study on characteristics of in vitro release and transdermal penetration of Danhuang gel. Method: Modified Franz diffusion cell was used

with berberine and chrysophanol as indexes

in vitro drug release and percutaneous penetration laws of index components were described by kinetic model. Result: Release of chrysophanol could be fitted best by zero-power kinetics model

but berberine by Ritger-Peppas model;Penetration of chrysophanol and berberine in vitro skin were best by fitting for one-power kinetics model;Relevant linear equation of in vitro release and transdermal penetration for chrysophanol could be described as Y=0.468 7X+4.972 2 (r=0.966 4)

berberine as Y=0.666 9X+2.487 4 (r=0.974 0)

and in vitro release rate was higher than in vitro transdermal rate of two index components in Danhuang gel. Conclusion: In vitro release and transdermal penetration of berberine and chrysophanol had a good linear correlation.