Objective: The paper evaluates the impact of national centralized volume-based procurement (NCVBP) on the renewal period in public medical institutions. Methods: Data on the procurement records of drugs from January 2018 to December 2020 were obtained from the China Drug Supply Information Platform (CDSIP). The change of purchase volume, purchase expenditure and daily cost of drugs with different winning bids in the public medical institutions from 7 pilot cities was analyzed. Interrupted time-series analysis (ITSA) with two intervention points was used in this study. Results: The DDDs level of generic drugs passing the consistency evaluation of quality and efficacy (CEQE) which won the bid during the agreement period but failed in the renewal period changed significantly during the agreement period (β₂=18713.23,p<0.001). The change in the DDDs level (β₄ =-22287.48,p=0.002) , the trend (β₅=-1943.60,p=0.022) , and the level of purchase expenditure (β₂=-21869.97,p=0.002) was significant in the renewal period. The DDDs level of drugs which failed in the bid during the agreement period but won the bid during the renewal period changed significantly during the renewal period (β₄=19442.77,p<0.001), and the change of purchase expenditure (β₄=8840.89,p<0.001) was significant. The results showed that purchase expenditure (β₂=-89005.99,p<0.001) of generic drugs which didn’t pass the CEQE in selected drugs decreased during the agreement period. The trend of purchase expenditure (β₄=2538.91,p=0.046) and its proportion (β₄=0.52,p=0.011) was upward in the renewal period. Conclusions: The daily average cost of unapproved generic drugs should be monitored, and the mechanism for listing and unlisting unapproved generic drugs should be improved. We should monitor whether there is an unreasonable increase in the daily cost of drugs failed in the agreement and renewal period, also we should adhere to the policy of centralized NCVBP and improve supporting measures.