COVID-19 which outbroke in early 2020, is the most significant public health emergency in recent years. Excavating the characteristic and evolution tendency of social public opinion about medical supplies during the epidemic period will help us understand the evolution of this emergency and the social response mechanism. This study conducts research from the perspective of topic evolution and event structure. Based on the ``mask" related news corpus, this study uses the LDA topic model to dig some hot topics from the news under different periods during the epidemic. Therefore, the relationship and evolution path of some main topics, which are about the social epidemic situation, social epidemic prevention, mask production and supervision, and the import and export of mask, are analyzed. In view of the customs seizures in the import and export of masks, this study builds a co-occurrence keywords network based on the keywords in the events, learns the main four types of seizure events, and obtains the relationship between the customs and the seizure event keywords through the construction of the bipartite networks of custom-keywords.