Abstract: Objective：To investigate the histomorphological changes of the keratocystic odotogenic tumor after decompression. Methods：The histomorphologyical changes of 22 KCOT tissue slices stained with hematoxylin and eosin before decompression and after curettage were observed ，including the epithelial modality，the depth of the epithelium and connective tissue，the degree of inflammation infiltration adjective of the basal layer，then statistic analysis were made. Results：54.5 percent of the cases were found lost of epithelial para and localized hyperplasia with rete pegs, in addition, the thickness of both epithelium and connective layer increased statistically after decompression (P <0.05) and the degree of inflammation infiltration also intensified dramatically (P<0.05).Conclusions：The histomorphological features of KCOT have changed remarkably after decompression, appearing as the thickened linings and intensified inflammation infiltration, further research is needed to explain the mechanism of the above-mentioned changes.