CtDNA detection as a noninvasive detection method, can truly reflect the real tumor tissue gene mutation map and frequency, is the evaluation of therapeutic effect and the important monitoring indicators of clinical follow-up after treatment. The second generation of high-throughput gene sequencing (NGS) is an important means of detecting ctDNA, which can detect trace ctDNA from smaller plasma samples. The ctDNA dynamic monitoring of stage I non-small cell lung cancer (NSCLC) was performed by the second generation gene sequencing (NGS) technique to verify the prognostic predictive effect of ctDNA in stage I NSCLC patients without radiotherapy and targeted therapy.