Abstract: OBJECTIVE To compare transdermal penetration enhancement and cytotoxicity of nine oxygen-containing monoterpenes from essential oils. METHODS The nine most common oxygen-containing monoterpenes from herbal essential oils， which have penetration enhancement reports were selected. They are 1，8-cineole， 4-terpineol， camphor， menthol， α-terpineol， carvone， linalool， geraniol and citral. Its effect of permeation enhancement on ibuprofen and cytotoxicity on HaCaT cells were compared. RESULTS The nine oxygen-containing monoterpenes all promoted the transdermal absorption of ibuprofen evidently， and the cytotoxicity were much lower than that of the classical chemical penetration enhancer azone. 1，8-cineole has the best effect. It was found that the cyclic oxygen-containing monoterpenes（1，8-cineole， 4-terpineol， camphor， menthol， α-terpineol， carvone）have better penetration enhancement effect than that of the chain oxygen-containing monoterpenes（linalool， geraniol， citral）. There was no significant difference between the cytotoxicity of cyclic and chain oxygen-containing monoterpenes. CONCLUSION Cyclic oxygen-containing monoterpenes are more suitable for the development of penetration enhancers.