SNS, namely social networking sites, has become one of the most effective and fast channels of information diffusion and dissemination. As an influential way of online marketing, SNS has been increasingly used by tourism organizations and enterprises to shape their destination image. On the basis of previews literature of destination image and SNS, this paper used the text analysis software ROST Content Mining (ROST CM) System to do a case study of the SNS destination marketing of Singapore on Chinese market. The authors analyze the text related to Singapore tourism on the major SNS in mainland China: Renren, Sina Weibo, and Douban, through word frequency analysis and the social semantic network, to summarize the destination image of Singapore on SNS. The paper also focuses on the difference of image building by official and individual SNS. Results found by this paper can be used by the relevant tourism organizations and enterprises to improve their destination marketing and image building on SNS channels.