Abstract: The objective of sponsoring large-scale sports events is to enhance the market value of enterprises. In this paper, the event research method was applied to investigate the abnormal return fluctuations of the stock price at two phases, which were the announcement of sponsorship by Chinese sponsors of the 2018 World Cup in Russia and the opening day of the games. It was found that the abnormal returns of stocks in the event window of sponsorship announcement were significantly positive, while the abnormal returns of stocks in the event window of opening day were significantly negative, and the market value of firms decreased.In addition, Baidu search index was used to study the impact of the online attention on the abnormal returns of the sponsors. The relationship between Baidu search index and abnormal stock returns shows that sponsors' day-by-day abnormal returns correlate strongly with Baidu search index. The results indicate that sponsors should pay attention to the short-term and long-term effects of sponsoring large-scale events, prevent over hype, and actively use marketing mix to expand the impact and benefits of sponsorship.