Abstract: OBJECTIVE To investigate the irriration and organic morphological variation of Centipeda minima oil microemulsion-based thermosensitive hydrogel in rats. METHODS The rats were divided into 3 groups, including the normal control group, the blank microemulsion-based thermosensitive hydrogel group and the Centipeda minima oil microemulsion-based thermosensitive hydrogel group, investigating the morphological changes of main organs of rats after nasal administration, to evaluate the preliminary security of Centipeda minima oil microemulsion-based thermosensitive hydrogel. RESULTS Rat nasal mucosa tissue sevtions showed that there was completed cilia and normal mucous cells in the nasal septum cartilage after nasal administration of saline solution, blank gel and Centipeda minima oil microemulsion-based thermosensitive hydrogel, without obvious vascular congestion, necrosis, shedding, bleeding of mucosa and tissue. The histological sections of main organs of the rats after nasal administration of Centipeda minima oil microemulsion-based thermosensitive hydrogel revealed that there was no cell structural changes, such as the normal group and the blank gel group. CONCLUSION The Centipeda minima oil microemulsion-based thermosensitive hydrogel is approved to have no obvious irritation to the nasal mucosa and no obvious damage on main organs of rats, and it is suggested that the application of Centipeda minima oil microemulsion-based thermosensitive hydrogel is safe.