To investigate the clinical value of CTR, CEA, histological type, Ki-67 and EGFR in detecting pathological lymph node metastasis (pN) in clinical stage IA (cIA) lung adenocarcinoma and to construct a pN Nomogram model. A total of 374 cIA lung adenocarcinoma patients who had undergone thoracoscopic radical resection with Systematic mediastinal lymph node dissection (SMLD) in the Department of Thoracic Surgery of the Affiliated Hospital of Qingdao University between January 2018 to January 2020 were retrospectively reviewed. The patients were divided into pN(+) and pN(-) groups. Univariate and multivariate Logistic regression analyses were used to analyze the independent risk factors of pN in lung cancer patients. The ROC curve was used to compare the accuracy of CTR, CEA and Ki-67 in predicting pN. R software was used to construct a Nomogram prediction model based on multivariate Logistic regression analysis of the pN risk. The C-index was calculated, and a calibration curve was drawn to judge the calibration degree of the model. The preoperative and intraoperative examinations showed that CTR (OR 570.406, P＜0.001), CEA (OR 1.239, P＜0.001) and micropapillary adenocarcinoma (OR 86.712, P＜0.001) were independent risk factors of pN. Immunohistochemical analysis and gene detection showed that Ki-67 index (OR 4.832, P＜0.001) and EGFR mutations, such as exon 19 (OR 10.319, P＜0.001), exon 21 (OR 7.163, P＜0.001) and exon 19+20 mutations (OR 570.406, P＜0.001), were significant factors in predicting pN. CTR, CEA, histological type, Ki-67 index, and EGFR mutations are the predictive factors of pN in cT1a-3aN0M0 lung adenocarcinoma patients. SMLD is recommended to improve patients’ postoperative survival rate when preoperative CTR≥0.775, CEA＞2.52μg/L or intraoperative rapid freezing pathology shows micropapillary components.