Abstract: Objective To screen and identify differential expression proteins,and to obtain theoretical data for studying human stage Ⅰ lung adenocarcinoma molecular mechanism and finding early biomarker. Methods The total proteins of 12 human stage Ⅰ lung adenocarcinoma tissue and normal tumor-adjacent tissue were separated,using 170mm long immobilized pH gradient(IPG) gel strips,pH3-10,for the first dimension and homogeneous SDS-polyacrylamide gel electrophoresis(SDS-PAGE)(12%T) for the second dimension.The differen expression proteins were analyzed with PDQuest image analysis sof tware, then identified using mat rix-assisted laser desorption/ ionization time of flight mass spect romet ry (MAL-DI2TOF2MS) and database searching. Results 　The well-reproducible -2DE gel patterns of human stage Ⅰlung adenocarcinoma and normal tumor2adjacent tissue were established and 26 differential proteins were screened. Nine of 26 differential protein spot s were cut out f rom the preparation gels and were iden-tified with MALDI-TOF-MS. Comparing with the protein database, four candidate proteins were identified with MS. They were 60S acidic ribosomal protein P2, Cathepsin B precursor, Apolipoprotein A2I precur-sor and La 4. 1 protein. Conclusion 　In this study, 2-DE gel images of human stage Ⅰlung adenocarcino-ma and paired normal tumor-adjacent tissue were established successfully, and identified 4 differential pro-teins. These data will be helpful for studying human lung adenocarcinoma molecular mechanism and screening early biomarker.