This study aims to evaluate the utility of combined plasma SHOX2 and PTGER4 gene methylation analysis as a dynamic biomarker for monitoring minimal residual disease (MRD) and predicting recurrence in postoperative non-small cell lung cancer (NSCLC) patients. The primary objective is to determine whether serial methylation assessment can guide personalized adjuvant therapy decisions by identifying high-risk individuals, thereby potentially reducing overtreatment or undertreatment. Stage I-IV NSCLC patients undergoing surgical resection were enrolled. Peripheral blood was collected longitudinally for circulating tumor DNA (ctDNA) methylation testing: preoperatively, postoperatively at 3 days, 1, 3, 6, 9, 12, 18, and 24 months, and upon radiographic recurrence. The dynamic changes in SHOX2/PTGER4 methylation levels and conventional tumor marker positivity rates were analyzed. Comprehensive statistical analyses were performed: Correlation between methylation levels and radiographic findings was assessed using Pearson/Spearman tests; predictive accuracy for recurrence was evaluated via ROC curve analysis; patients were stratified into methylation-based risk groups; survival differences were compared using Kaplan-Meier curves with log-rank testing; independent predictive value was determined through multivariate Cox regression adjusting for clinicopathological confounders. Final efficacy assessment integrated ctDNA positivity timing, disease-free survival (DFS), and overall survival (OS) metrics. This prospective biomarker study seeks to validate a novel epigenetic approach for postoperative management, potentially establishing ctDNA methylation monitoring as a standardized tool for MRD detection and recurrence risk stratification in resected NSCLC.