Objective Non-small cell lung cancer ( NSCLC) cells are relatively resistant to chemotherapy, and the outcomes are not always satisfactory. This study was designed to explore the relationship between the content of Ku80 protein of human lung cancer cells and their sensitivity to cisplatin.Methods The lung cancer cells isolated frommalignant pleural effusion samples frompatients with primary lung cancer were cultured in vitro. The sensitivity to cisplatin was tested with the method of CCK-8 expressed as half maximal inhibitory concentration ( IC50 ) . The relative content of Ku80 protein was determined by Western blot. The correlation between sensitivity to cisplatin of lung cancer cells and the relative content of Ku80 protein was analyzed. Results The IC50 of NSCLC group was significantly higher than that of SCLCgroup [ ( 4. 40 ±3. 39) mg/L vs. ( 1. 02 ±0. 54) mg/L, P lt; 0. 001] . The relative content of Ku80 protein of NSCLC group was statistically higher than that of SCLC group [ ( 0. 80 ±0. 45) vs. ( 0. 48 ±0. 25) , P lt;0. 05] . The correlation coefficient between content of Ku80 protein and IC50 was 0. 618 ( P lt; 0. 001) .Conclusions The content of Ku80 protein of NSCLC patients is higher than that of SCLC patients. Itmay be one of the mechanisms contributing to chemotherapeutic resistance of NSCLC. There is a negative relationship between Ku80 protein content of cancer cells and their sensitivity to cisplatin suggesting that the content of Ku80 protein may be served as a candidate index for predicting sensitivity of lung cancer cells to cisplatin.