As a key part of the strategic purchasing policy for medical insurance, centralized volume based procurement has become a focus of industry attention for its profound impact on the pharmaceutical industry. Taking the "announcement day" event of traditional Chinese patent medicines and simple preparations medical insurance centralized purchase as the research event, we use the A-share market share price data to test the spillover effect of centralized purchase policy. Research has found that key information on centralized procurement, such as procurement rules and winning bid results, have an impact on capital market information, leading to policy spillover effects. Heterogeneity analysis shows that the publication of procurement rules has a negative effect. The centralized purchase of traditional Chinese patent medicines and simple preparations has had an inter industry contagion spillover effect on other sub industries, but the duration is limited. The winning results have a positive effect. The winning companies have had an intra industry contagion spillover effect on the unsuccessful companies, but the unsuccessful companies have more significant positive fluctuations.