Objective: The paper analyzes the impact of the centralized procurement policy on pharmaceutical companies' drug sales and provide a theoretical basis for the improvement of the policy. Methods: The interrupted time series method was used to analyze the sales of centralized drug varieties and alternative drugs varieties by pharmaceutical companies before and after the implementation of the centralized procurement policy. Results: After the implementation of the centralized procurement policy, the procurement volume of the selected enterprises increased by 163.28% and the proportion of procurement volume in all enterprises increased from 37.45% to 86.45%, while the procurement volume of unsuccessful enterprises decreased by 75.30% and the proportion of procurement volume in all enterprises decreased from 62.55% to 13.55%. Among the selected companies, the procurement volume of centralized drug varieties of non-top 100 enterprises increased by 313.27%, while the procurement volume of centralized drug varieties of top 100 enterprises increased by only 5.76%. The interrupted time series analysis revealed that in the non-supply regions, the procurement volume of selected companies had significant immediate changes (β2=-58.727, P<0.001) and the long-term trend was downward after the policy intervention (β3=-4.550, P=0.010). Conclusion: The policy has led to significant change in market share for the selected and unsuccessful companies in centralized drug varieties, but with limited impact on alternative varieties. The procurement volume of the selected top 100 companies has seen small growth. The procurement volume of unsuccessful enterprises shows a long-term downward trend. The sales of drugs by selected enterprises in non-supply areas have significantly decreased. Government departments should pay continuous attention to the reasonable profit demands of selected enterprises, guide them to change marketing strategies, and ensure the stable supply of selected products.