OBJECTIVE To analyze the impact of intergenerational substitution effect of the drugs with the same indication on fund expenditures for national medical insurance for this indication in China， taking national medical insurance negotiated drugs for non-small cell lung cancer （hereinafter referred to as “NSCLC national negotiation drugs”） as an example. METHODS The sales amounts of 15 types of NSCLC national negotiated drugs in secondary and tertiary public hospitals across seven sample provinces from 2017 to 2023 were collected from the Pharmaceutical Drug Database of the China National Pharmaceutical Industry Information Center. A sliding t-test and Mann-Kendall trend test were used to evaluate the trends in sales amounts and DDDs. Taking epidermal growth factor receptor（EGFR）-tyrosine kinase inhibitors （TKIs） and anaplastic lymphoma kinase （ALK）-TKIs as examples， the generational substitution characteristics of these drugs were analyzed. RESULTS The change points of sales amounts and DDDs differed slightly across provinces； the change points of sales amount were mostly concentrated between the first quarter of 2019 and the second quarter of 2020， while those for DDDs were primarily concentrated in the first to second quarters of 2021. In five provinces， i.e. Beijing， Heilongjiang， Jiangsu， Sichuan and Shaanxi， sales amounts showed no significant upward trend after the breakpoints （P＞0.05）， whereas in Guangdong and Hubei， both sales amounts and DDDs continued to rise significantly following the breakpoints （P＜0.05）. Since 2020， the growth in sales amounts of EGFR-TKIs had slowed. After 2021， the sales amounts and DDDs of first- and second-generation EGFR-TKIs declined， while third-generation EGFR-TKIs showed clear substitution effects. The sales amounts of ALK-TKIs continuedto grow. However， the sales amounts and DDDs of first-generation ALK-TKIs had declined year by year， with second-generation ALK-TKIs demonstrating a significant substitution effect on first-generation ones， while third-generation ALK-TKIs had not yet shown a clear substitution trend. CONCLUSIONS With the annual access to and renewal of drugs in national medical insurance negotiations， the overall expenditure trend for NSCLC negotiated drugs comes to a plateau. The intergenerational substitution relationships of drugs with the same indication achieve a relative balance in fund expenditures for negotiated drugs with the same indication. It is recommended that pharmaceutical companies carefully consider their research pipelines， and that medical insurance authorities， during the renewal management process， pay attention to the impact of drug substitution effects on the overall actual expenditure of medical insurance funds for that specific target or the same indication， and scientifically evaluate the extent of price reductions during contract renewals.