As a core biomarker of non-invasive liquid biopsy, circulating tumor DNA (ctDNA) provides a breakthrough approach for minimal residual disease (MRD) monitoring in esophageal cancer. Esophageal cancer is clinically characterized by strong invasiveness, high postoperative recurrence rate, and poor prognosis. Traditional imaging and histopathological examinations are difficult to meet the clinical demand for accurate MRD identification due to limitations such as insufficient sensitivity and high invasiveness. This paper systematically reviews the biological basis and technical advances of ctDNA detection, focusing on the advantages and clinical application scenarios of core technologies including digital polymerase chain reaction, next-generation sequencing, and methylation detection. It further analyzes the core clinical value of ctDNA in esophageal cancer MRD monitoring, covering key directions such as early recurrence warning, dynamic evaluation of treatment efficacy, and optimization of individualized treatment strategies. Meanwhile, the main challenges currently faced, including insufficient technical standardization, interference from tumor heterogeneity, and lag in clinical translation, are discussed, and future development trends such as multi-omics integration and artificial intelligence-assisted diagnosis are prospected. This review aims to provide an academic reference for the precise clinical management of esophageal cancer MRD, promote the standardized application and translation of ctDNA technology in clinical practice of cardiothoracic surgery, and ultimately improve the survival prognosis of patients.