Abstract：Objective：To explore the value of single cell gel electrophoresis (SCGE) assay for detecting DNA double-strand breaks (DSBs) levels of lymphocytes in the diagnosis and treatment of the patients with non-small cell lung cancer (NSCLC). Methods：Blood samples from 132 NSCLC patients, 39 benign lung disease patients and 42 normal individuals were collected and lymphocytes were isolated. DSBs levels were detected by SCGE assay. The relationship between percentage of tail DNA (%Tail DNA) together with Olive tail moment (OTM) and the pathological types, clinical stages and therapeutic efficacy of NSCLC patients were investigated. Results：The values of %Tail DNA and OTM with SCGE assay in NSCLC group were significantly higher than those of benign lung disease group（t=2.637, 2.460，P＜0.05）and control group（t=8.832, 9.682, P＜0.05). No correlation of values of %Tail DNA and OTM with pathological type and clinical stages of NSCLC was showed (P＞0.05). The values of DSBs after treatment were significantly lower than those before treatment (P＜0.05). Conclusion：DSBs of DNA in lymphocytes detected with SCGE assay could improve the diagnosis for NSCLC and become a novel monitor of therapeutic efficacy.