Objective To investigate the effect of Sindilizumab combined with PC regimen (pemetrexed disodium + carboplatin) in the treatment of advanced lung cancer and its effect on serum tumor markers. Methods 92 patients with advanced lung cancer admitted to our hospital from January 2023 to December 2024 were selected as the study objects. Patients were divided into control group (n=46) and study group (n=46) by random number table method. The control group was treated with PC regimen. The study group was treated with Sindilizumab combined with PC. Disease control rate, serum tumor markers [CEA, CA199, CA125] levels, immune function [T cell subsets (CD3+, CD4+)] and incidence of adverse reactions were analyzed and compared between the two groups. Results The disease control rate of the study group was significantly higher than that of the control group (P < 0.05). After treatment, the levels of CEA, CA199 and CA125 in both groups were significantly lower than before treatment, and the levels of CEA, CA199 and CA125 in the study group after treatment were significantly lower than those in the control group (P < 0.05). After treatment, the levels of CD3+ and CD4+ in both groups were significantly higher than before treatment, and the levels of CD3+ and CD4+ in the study group after treatment were significantly higher than those in the control group (P < 0.05). There was no significant difference in the incidence of adverse reactions between the two groups (P > 0.05). Conclusion Sindilizumab combined with PC regimen in the treatment of advanced lung cancer can improve the therapeutic effect, inhibit tumor progression, and restore immune function, with high safety.