Objective: The paper analyzes and compares the differences in the contribution rate of different levels of public medical institutions to the change of drug procurement volume after the national centralized volume-based procurement (NCVBP). Methods: Data on the drug procurement records of from January 2018 to December 2020 were obtained from the China Drug Supply Information Platform (CDSIP). The contribution rate of different levels of public medical institutions on drug procurement volume and procurement expenditure from 7 pilot cities was analyzed. Results: The contribution rate of tertiary medical institutions was the highest (58.03%) during the pilot period on the increase in the purchase volume of centralized varieties, but the contribution rate of primary medical institutions was the highest (103.29%) during the continuation period. The contribution rate of primary medical institutions during the pilot period and the continuation period was the highest on the increase in the procurement volume of substitute varieties (54.87% and 72.88%). The contribution rate of primary medical institutions during the pilot period was the highest (45.62%) on the increase in the procurement expenditure of B01 antithrombotic bid-winning drug. The contribution rate of primary medical institutions during the pilot period and continuation period was the highest on the increase in the procurement volume of C08 calcium channel blocker, C09 acting on the renin-angiotensin system bid-winning drug. The contribution rate of tertiary medical institutions during the pilot period and the continuation period was the highest on the increase in the procurement volume of L01 anti-tumor bid-winning drug (89.21% and 61.85%). Conclusion: During the continuation period, the contribution rate of primary medical institutions to the increase in procurement volume increased during the continuation period. The procurement volume of some therapeutic drugs has increased, among which the contribution rate of primary medical institutions was the highest.