OBJECTIVE：To ev aluate the economics of pembrolizumab versus first-line chemotherapy in the treatment of advanced non-small cell lung cancer with high programmed cell death protein ligand 1（PD-L1）expression from the perspective of Chinese healthcare system. METHODS ：Published KEYNOTE- 042 clinical trial data and relevant literature data were used to establish a Markov model to evaluate the economics of pembrolizumab versus first-line chemotherapy with a 20-years horizon and a 3-week cycle length ，discounting costs and utilities using a discount rate of 5％. One-way sensitivity analysis and probabilistic sensitivity analysis were used to evaluate the stability of the model results. RESULTS ：The base-case results showed that pembrolizumab yield additional 1.62 QALYs more than first-line chemotherapy ，with an incremental cost of 54 648 yuan；the incremental cost-utility ratio was 33 686 yuan/QALY，which was lower than the willingness-to-pay threshold （WTP）in China. The results of one-way sensitivity analysis showed that the price of nivolumab ，the price of pembrolizumab and the proportion of patients who received second-line immunotherapy in first-line chemotherapy group had the greatest impact on the results. The results of probabilistic sensitivity analysis showed that the probability of pembrolizumab to be cost-effective gradually increased within the WTP of 0-140 000/QALY. When WTP was 70 892 yuan/QALY（one time of the per capita GDP of China in 2019），the probability of pembrolizumab to be cost-effective was 95％. When WTP beyond 100 000 yuan/QALY，the probability of pembrolizumab to be cost-effective was 100％. CONCLUSIONS ：Pembrolizumab has economic advantages than first-line chemotherapy in the first-line treatment of non-small cell lung cancer with high PD-L 1 expression in China.