Abstract: The objective of this study was to characterize the effect of azone,a commonly used penetration enhancer,on the in vitro percutaneous absorption of a compound traditional Chinese medicine ointment through horse skin.The ointment was prepared with the concentrates obtained with water-extraction and alcohol-precipitation method,and the different concentrations of azone (2%,4%,5.5% and 7%) were supplemented in the prepared ointment,respectively.The icariin,one of the main active ingredients of the prepared ointment,was used as an indicator to assess the penetration enhancing effect of azone.The content of icariin in penetrating fluid from horse skin treated by the smart drug transdermal device was determined using the microplate reader.The best penetration effect was observed when 5.5% of azone was added as a penetration enhancer in the ointment.This study provides a theoretical basis for the selection of penetration enhancers used in traditional Chinese medicine ointment for equine,and also provides a safer,more effective and more stable administration route for investigation of transdermal delivery system of compound traditional Chinese medicine.