Objective: To detect expression of PTEN gene at lung cancer tissue and probe the relationships between PTEN expression and lung cancer. Methods: The expression of PTEN DNA was detected by in situ PCR. Results: ①The expression of PTEN DNA were mainly situated in nucleus,and partly in cytoplasm. The positive signal were buffy and suffusing distribution. ②The expression of PTEN gene were different in gender,but the difference were minute. ③The positive expression rate of PTEN DNA in NSCLC was higher than that in SCLC. ④The positive expression rate of PTEN in poorly differentiated lung cancer tissue was lower than that in secondary-differentiated and well-differentiated tissue. ⑤Expression of PTEN in 19 patients with lymph node metastasis was obviously lower than that in 37 without no-lymph node metastasis. Conclusion: Expression of PTEN gene in lung carcinoma was lower than that in normal lung tissue,which indicated that down-regulation expression of PTEN possibly play an important role in carcinogenesis and development. And expression of PTEN has no correlation with gender of lung cancer patients,while correlated with classify,differentiation,clinical stage and lymph node metastasis of lung cancer.