Abstract: Objective 　To investigate the relationship and clinical significance between the DC subset s and nature killer cell of patient s with advanced non2small cell lung cancer. Methods 　Flow cytomet ry was used to detect DC subset s, N K cell percent and Interleukin212 in the peripheral blood of 40 patient s with advanced NSCLC and 10 healthy cont rols. Results 　The expression of CD11c + DC(0. 66 ±0. 24) % in pe2 ripheral blood in advanced NSCLC patient s, was decreased more significantly than that in normal cont rols (1. 38 ±0. 18) %( P < 0. 01) . The expression of CD123 + DC in peripheral blood in advanced NSCLC pa2 tient s was (0. 28 ±0. 17) %, with no significant difference compared with that in cont rols (0. 27 ±0. 11) % ( P > 0. 05) . The percentage of N K cell of patient s were lower than cont rol ( P < 0. 05) . The plasma con2 cent ration of IL212 of patient s was significantly decreased ( P < 0. 01) . The correlation analysis showed that N K cell percentage was negatively correlated to percentage CD123 + DC percentage ( P < 0. 05), and positive correlated to CD11c + DC and IL212 ( P < 0. 01) . The expression of DC subset s had correlation with KPS and chemotherapy history ( P < 0. 01), N K cell percent just had correlation with age. Conclusion 　The advanced NSCLC may induce significant decreasing expression of DC1, blocking secretion of lnter2 leukin212 and may induce significant decreasing activity of N K cell. There is a much closed relationship between the expression of DC subset s and N K cell percent of patient s as well as the clinical biological be2 haviors of patient s with advanced NSCLC.