Abstract: 【 Purpose/significance】 Using the content posted by users on social media platforms as data sources, we analyze the evolu⁃ tion of public perceptions of vaccine policies in public health emergencies in two dimensions: thematic and emotional, which can pro⁃ vide a basis and direction for multiple subjects such as the government and public health departments to carry out accurate vaccine propaganda, popularization services, and public opinion guidance in different life cycle stages【. Method/process】 With the perspective of cognitive-emotional-intentional theory, the study integrates SKEP sentiment analysis pre-training model and LDA topic model based on TF-IDF algorithm to calculate the public's sentiment tendency towards vaccine policy at different life cycle stages of public health emergencies, to explore the potential topics and focus of attention of users at different sentiment tendency stages, and then visu⁃ alize the public's cognitive evolution process towards vaccine policy.【Result/conclusions】 The results of the study showed that the public's emotional tendency trend showed alternating fluctuations of positive and negative emotions, the initial period involved seven topics, the outbreak period involved six topics and generated a large amount of information and emotional expressions, and the spread⁃ ing period involved 6 topics, and the process of topic evolution in these three stages reflected both continuity and distinctiveness; the fo⁃ cus of public attention throughout the cognitive process mainly included 3 aspects: basic information about vaccines, interpretation and implementation of vaccination policies, and vaccination status【. Innovation/limitation】 Only positive and negative sentiments were classi⁃ fied in the analysis of public sentiment tendencies, and further fine-grained analysis will be done for sentiment types in future studies.