Abstract: Objective: To investigate the change of p16 protein expression in esophageal carcino-ma and precancerous lesions and to explore the relationship between p16 protein and esophageal car-cinoma. Methods: Expression of p16 protein in specimens from 94 cases with esophageal carcinoma were measured qualitatively by immunohistochemistry and quantitatively by flow cytometry (FCM) anal-ysis. Results: a) With the increase of histopathologic grade, the expression p16 protein reduced gradu-ally; b) The result of immunohistochemical method: there was no remarkable correlation between normalgroup and the groupⅠwith atypical hyperplasia (P>0.05). There was a significant differences (P<0.05)in the p16 protein expressions of the normal group and other groups. There was a significantly statisti-cal difference (P<0.05) in the p16 protein expressions in the group of squamous cell carcinoma, normalgroup and the groupⅠwith atypical hyperplasia. There was no remarkable correlation between the group of squamous cell carcinoma and other groups (P>0.05); c) The result of flow cytometry analysis: therewas a significant difference (P<0.001) in p16 protein expression of the group Ⅱwith atypical hyperpla-sia and normal group. There was a significant differences (P<0.05) in the expression of the group of atypical hyperplasiaⅡand Ⅲ. There was no remarkable correlation between the group of atypical hy-perplasia Ⅲ and squamous cell carcinoma (P>0.05). Conclusions: With the increase of histopathologic grade, the expression p16 protein decrease gradually. The negative expression of p16 protein takesplace early and possibly plays an important role in occurrence of esophageal cancer.