In recent years, food safety incidents occur often, which have negative influence on the enterprise, especially the shares of listed companies. According to the number of news about liquor plasticizer event collected by Baidu, the study did a quantitative research on the relation between media coverage and stock prices. The study found that a large number of persistent reports would make negative effects on stock prices of sample companies during a long time. The conclusion has important significance for the decision-making of public administrative department and firms.