In order to sway the public opinion effectively, Latent Dirichlet Allocation(LDA) topic model is used in this paper to visualize and analyze the influence of official information on online public opinion. Taking the event "Terminal High Altitude Area Defense(THAAD) in South Korea" as a case study, this paper takes the topics of relevant data of the event as an example to calculate the similarity between the topics and analyze the key events. The visual analysis of the examples shows that the official press conference has a significant effect on the online public opinion in two days to four days, pushing the related topics to the climax or bottom. Moreover, in the process of event development, the similarities tend to be basically the same. This visualization can provide reference to relevant departments on the regulation of online public opinions, that is, it is most appropriate to guide and regulate online public opinion within 2 days to 4 days
before the expected time.