Objective To explore and evaluate the economy of pembrolizumab combined chemotherapy in the first-line treatment of advanced malignant pleural mesothelioma from the perspective of China's healthcare system,and to provide pharmacoeconomic evidence and reference for clinical medication and related health decisions.Methods A partition survival model was constructed based on the IND227 study data,with 21 d as the model period and simulated to 99％of patients died.The model output index was the quality-adjusted life year(QALY).The cost-utility analysis was used to evaluate the economics of combination chemotherapy for advanced malignant pleural mesothelioma by chemotherapy alone.Further,the robustness of the basic analysis results was proved by univariate sensitivity analysis and probabilistic sensitivity analysis.Results The results of basic analysis showed that compared with chemotherapy alone,the incremental cost-utility ratio(ICUR)of pembrolizumab combined with chemotherapy was 1 447 296.58 yuan/QALY,which was greater than 3 times China's per capita GDP(268 074 yuan/QALY)in 2023 as the willingness-to-pay(WTP)threshold,which was not economical.In the case of receiving charity drug donations,the ICUR was 102 236.18 yuan/QALY,which was below the WTP threshold.The results of univariate sensitivity analysis showed that the cost of pembrolizumab,utility discount rate and supportive therapy in the chemotherapy group had more significant effects on the results.The results of the probability sensitivity analysis showed that the basic analysis results showed good robustness.Conclusion At a WTP threshold of 3 times China's per capita GDP in 2023,pembrolizumab combined with chemotherapy is not cost-effective for treating advanced malignant pleural mesothelioma.However,if the patient receives charity donations,combination of pembrolizumab and chemotherapy is more cost-utility.