On September 16, 2018, Typhoon Mangkhut, with record sustained winds of an estimated 110-115 mph, struck southern China, causing tremendous damage to the region. Since then, there have been many online discussions about the typhoon and how the government responded to it. In the domain of emergency response to disasters, the increasingly prominent role of social websites has been confirmed. This paper presents a case study of public attitudes and opinions regarding Typhoon Mangkhut that were collected from the Sina Weibo and WeChat websites, as well as from news websites. We then present a method for managing false online information in the wake of such natural disasters. The method consists of four phases: information extraction, sentiment recognition, opinion classification, and simulation analysis. In the last phase, a simulation experiment was conducted to assess how false information spreads. We used three scenarios in the simulation-namely, a real scenario, an isolation scenario, and an embedment scenario, each of which was based on a scale-free network based on a scale-free network. The results showed that the embedment strategy better controlled the transmission of false information than did the isolation strategy. In addition, we have provided some practical suggestions. This paper contributes to the literature on the emergency management of natural disasters.