Abstract: Objective To investigate the relationship between protein expression of PTEN and differentiation, infiltration and metastasis of esophageal squamous cell carcinoma (ESCC)． Methods The immunohistochem isty SP method was used to detect the protein expression of PTEN in 50 cases of ESCC tissues and adjacent noncancerous tissues． Then, cell biological experiments such as migration and invasion experiments were performed in ESCC cell lines to explore their functions in tumor progression． Results The positive incidence of PTEN in ESCC tissues was 60%, while in adjacent noncancerous tissues, it was 90%． The differences were statistically signif cant (Z=4．078, P< 0．001)． The protein expression of PTEN was positively correlated with its differentiation．Furthermore, the protein expression of PTEN had a negative correlation with lymph node metastasis，depth of invasion and TNM．Correspondingly, overexpression of PTEN remarkably inhibited the ability of migration and invasion in ESCC cells． Conclusion The decreased protein expression of PTEN plays an important role in the metastasis of ESCC．