Objective：The aim of this study was to identify the key genes and uncover the potential molecular mechanisms of lung adenocarcinoma（LAC）. Methods：In our study，three microarray data sets of LAC genes，including 156 cases of LAC and 106 cases of normal lung tissue，were used to screen the potential key genes. Results：First，341 overlapping differentially expressed genes（DEG）were found by microarray data analysis. The main biological processes of DEG enrichment were extracellular matrix tissue，regulation of chemical kinase-mediated signaling pathways，cell response to transformed growth factor stimulation，extracellular matrix assembly，and regulation of angiogenesis. Next，10 key genes were screened out by using protein protein interaction（PPI）network，including 8 genes AURKA（aurora kinase A），CDC20（cell division cycle 20），CDH5（cadherin 5），COL1α1（collagen I，α1），EDN1（endothelin 1），MMP9（matrix metalloprotein 9），PECAM1（platelet endothelial cell adhesion molecule 1），SPP1（secreted phosphoprotein 1），which were correlated with the prognosis of LAC. Additional，CDC20 has the highest correlationship with the prognosis of LAC. The subgroup analysis showed that expression of CDC20 in all age groups of LAC patients increased significantly compared with nomal control；expression of CDC20 in tumor stage Ⅰ is lower than tumor stage Ⅱ，Ⅲ，Ⅳ；expression of CDC20 in aciner subtype，solid subtype，mixed subtype，clear cell subtype was higher than other subtypes；expression of CDC20 in LAC patients with smoking was lower than the non-smokers. Furthermore，the results by immunohistochemical showed that expression of CDC20 in LAC tissues was significantly higher than that in normal lung tissues，in acinar subtype and solid subtype was higher than other subtypes. Conclusion：CDC20 is high expressed in LAC，which is correlated with poor prognosis of LAC. CDC20 might be a potential biomarker and therapeutic target for LAC.