Abstract: Objective : To investigate the expression of vacuolar-H+-ATPase (V-ATPase) protein in non-small celllung cancer (NSCLC), to analyze the differences in V-ATPase expression among different pathological classifi-cations and grades, and to explore the correlation of V-ATPase expression with the chemoresistance ofNSCLC. Methods : We used immunohistochemistry and immunofluorescence to detect the expression of V-AT-Pase in 92 cases of NSCLC. The location of the protein was observed under light microscope and confocallaser scanning microscope. The chemoresistance of these cases was assayed by MTT method, and the corre-lation between the chemoresistance and V-ATPase expression in NSCLC were analyzed by statistics. Results :The V-ATPase protein was overexpressed at a rate of 71.43% in squamous cell lung cancer and 83.72% inlung adenocarcinoma, with a significant difference (P=0.000). In squamous cell lung cancer, the positive ex-pression rates of pathological grade II and II-III were 58.33% and 84.0%, respectively, with a statistical signifi-cance (P=0.014) The positive expression rates of moderately differentiated and low differentiated lung adeno-carcinoma were 76.70% and 100.0%, respectively, with a significant difference (P=0.012). The P values of thecorrelation tests between the chemosensitivity of cyclophamide, gemcitabine, adriamycin, paclitaxel, or cis-platin and V-ATPase expression in the NSCLC were all less than 0.05. The correlation coefficients(rs)were -0.714, -0.687, -0.612, -0.33, and -0.67, respectively. Conclusion : The V-ATPase protein is overex-pressed in NSCLC at a higher expression rate in lung adenocarcinoma than in the squamous cell lung cancer.The chemoresistance of NSCLC is probably correlated with the V-ATPase expression.