Abstract: Objective To investigate the expression of Ras p21 protein activator 1（RASA1）in non-small cell lung cancer（NSCLC）and the correlation with clinicopathological characteristics. Methods From Mar 2013 to Jan 2016, 202 cases of NSCLC tissues and 60 cases of adjacent normal tissues were collected. The expression of RASA1 in those above tissues was detected by immunohistochemical SP method and tissue microarray technique. The relationship between clinicopathological characteristics and the expression of RASA1 was analyzed. Results The high expression rate of RASA1 in NSCLC tissues was 74.8％（151／202），lower than 93.3％（56／60）of adjacent normal tissues with statistical significance（P=0.002）. The expression of RASA1 in NSCLC tissues was correlated with pathological types（P=0.000），but not with gender，age，lymphnode metastasis and clinical stage（P＞0.05）. Conclusion RASA1 was low expressed in NSCLC tissues，which may play a role in the occurrence and development of NSCLC as a potential tumor suppressor.