Abstract: Objective To establish the rabbit model of squamous epithelial precancerous lesion and observe the ultra-microstructure change of rabbit buccal mucosa epithelium in order to screen its revering drugs. Methods Sixty rabbits were divided into control group（n=12） and experimental group（n=48）.Pathological histology examination and electron microscopy were performed for the buccal mucosa of rabbits in experimental group 16 weeks after a solution and a drug membrane containing the carcinogen of dimethyl-benzanthracene（DMBA）were sprayed or pasted on it.Thirty-two rabbits were randomly selected from experimental group to carry out drug-reversing experiments 12 weeks after a solution and a drug membrane containing the carcinogen of DMBA were sprayed or pasted on it. Results Sixteen weeks after the rabbits were exposed to DMBA,their buccal mucosa became rough and congested with thickened local leukoplakia and Ⅱ-Ⅲ atypical hyperplasia in 64.6%（31/48） of the rabbits in experimental group.Disarranged atypical hyperplasia cells and edematous mitochondria were found in nuclei.Twelve weeks after drug-reversing experiment,the progressive rate of precancerous lesion was lower in rabbits exposed to all-transretinoic acid（ATRA） than in controls.Although Kanlaite could reverse the precancerous lesion but no significant difference was observed between those exposed to it and controls. Conclusion Squamous epithelial precancerous lesion model can be induced by DMBA and effectively reversed with ATRA.