Objective To explore the diagnostic value of circulating tumor cells (CTC) measured by magnetic nanoparticle method in lung cancer. Methods (1) We measured binding capability of A549 or NCI-H1965 cell lines with recognition peptide and capture efficiency by adding tumor cells into the whole blood of healthy human. (2) We measured CTC of 34 patients suspected with lung cancer, and the counting results of CTC were compared with the following pathological results. Results (1) The binding capability was 80.0%±6.0% for A549 and 70.1%±4.8% for H1957, while the capture efficiency was 57.3%±7.0% for A549 and 37.3%±6.1% for H1975. (2) CTCs were identified in 71.9% of patients with lung cancer. The specificity was 83.3%, and area under receiver operating characteristic (ROC) curve was 0.792 (P=0.003). Conclusion CTC measured by magnetic nanoparticle method has promising application in the diagnosis of lung cancer.