To study the suppressing effect of acetazolamide on tumor metastasis in vivo and observe the protein alteration of lung in mice bearing Lewis lung carcinoma. The functional role of aquaporin-1 (AQP1) was investigated in tumor tissues by SDS-PAGE and Western blot. The effect of acetazolamide on tumor metastasis was analyzed by Lewis-lung-carcinoma model. Differential protein was identified by SDS-PAGE, isoelectrofocusing (IEF) methods, and peptide mass fingerprinting (PMF). Acetazolamide (40 mg/kg/d po for 21 d) dramatically reduced the numbers of lung metastasis after sc inoculating Lewis lung carcinoma. The inhibition rate of lung metastases was 83.9 %. Simultaneously, the AQP1 protein level and actin-cytoplasmic in lungs containing metastatic tumor deposits were found to be higher than that in the normal tissue. After treated with acetazolamide for 21 d, the expression of AQP1 was obviously inhibited. Acetazolamide can suppress tumor metastasis, at least in part, by inhibiting the expression of AQP1. AQP1 and actin-cytoplasmic may be new prognostic molecules as well as new therapeutic targets for the prevention and treatment of metastatic tumor.