ObjectiveTo investigate the clinical significancy of K-ras gene mutation in peripheral blood free DNA in patients with non-small cell lung cancer (NSCLC). MethodsA total of 242 patients pathologically diagnosed with NSCLC in the Third People's Hospital of Chengdu were recruited between January 2013 and August 2015. Both tumor tissues and peripheral blood free DNA were collected for detection of K-ras gene mutation by mutant-enriched liquidchip technology. The detection rate was compared between these two kinds of samples. ResultsIn tumor tissues, the K-ras gene mutation was detected in 12 cases with a positive rate of 4.96%. While in peripheral blood samples, the K-ras gene mutation was detected in 10 cases with a positive rate of 4.13%. The detection yield of K-ras gene mutation in peripheral blood had a good consistency with that of lung cancer tissues (Kappa value=0.81). ConclusionK-ras in peripheral blood plasma free DNA can be a surrogate marker for tumor tissues' K-ras gene mutation in screening patients with NSCLC.