Objective:To investigate the effects of programmed death receptor 1(PD-1)inhibitor combined with low-dose chemotherapy on immune function and platelets in patients with advanced lung cancer.Methods:77 patients with advanced lung cancer were divided into control group(n=38)and observation group(n=39)according to different chemotherapy regimens.The control group was given conventional dose chemotherapy with paclitaxel and cisplatin,while the observation group was given PD-1 inhibitor(Trepelizumab)combined with reduced dose chemotherapy with paclitaxel and cisplatin,with one cycle every 21 d,and both groups were treated for three cycles.The clinical efficacy[objective response rate(ORR),disease control rate(DCR)],immune cell levels[CD3+cells,CD8+cytotoxic T cells(CD8+CTL),natural killer cells(NK)]and platelet(PLT)levels,adverse reactions and prog-nosis[progression free survival(PFS)and overall survival(OS)]before and after treatment were compared between the two groups.Results:There was no statistically significant difference in ORR and DCR between the two groups(P＞0.05).After treatment,there was no statistically significant difference in the levels of CD3+,CD8+CTL,and NK cells between the control group and before treat-ment(P＞0.05).The levels of CD3+cells,CD8+CTL and NK cells in the observation group increased and were higher than those in the control group(P＜0.05),while the level of PLT decreased but was higher than that in the control group(P＜0.05).There was no statistically significant difference in the incidence of leukopenia,neurotoxicity,liver damage and alopecia between the two groups(P＞0.05).The incidence of grade Ⅰ～Ⅱ gastrointestinal reactions and grade Ⅲ～Ⅳ anemia in the observation group were lower than those in the control group(P＜0.05).PFS and OS in the observation group were longer than those in the control group(P＜0.05).Conclu-sion;PD-l inhibitor combined with low-dose chemotherapy can enhance the immune function of patients with advanced lung cancer,re-duce the decline of PLT and improve the prognosis of patients better.