Objective: To prepare bakuchiol-baicalin compound microemulsions and investigate its in vitro transdermal diffusion characteristics. Method: With ethyl oleate as oil phase

tween-80 as emulsifier and polyethylene glycol-400(PEG-400) as co-emulsifier

aqueous phase was gradually added into mixture containing drug to produce bakuchiol-baicalin compound microemulsions.Morphology

particle size distribution and stability were characterized.Transdermal characteristics of bakuchiol and baicalin in solution and microemulsions were studied by modified Franze diffusion cell. Result: Clear and transparent microemulsion were prepared

they were showed nearly spherical under transmission electron microscope

particle size was (17.30±0.17)nm with excellent stability.Cumulative permeation amounts of baicalin in solution and microemulsions were (208.80±5.26)μg·cm-2 and (232.38±15.07)μg·cm-2 in 24 h

there were no significant difference of their transdermal characteristics.Cumulative permeation amounts of bakuchiol in solution and microemulsions were (324.81±56.63)μg·cm-2 and (721.30±108.88)μg·cm-2 in 24 h

compared with steady-state infiltration rate and apparent permeability coefficient in solution

these two parameters 5.0 times significantly improved. Conclusion: Delivery system of microemulsions can significantly improve percutaneous absorption.This study provides experimental foundations for development of a new preparation of bakuchiol-baicalin compound skin delivery system.