Eating disorder (ED) was not learned well in China. To contribute to an understanding of the prevalence of EDs in China and to identify individuals with ED tendencies, we randomly selected one million Sina Weibo (social media platform similar to twitter) users and collected all their postings related to ED keywords. Using thematic analysis and sentiment analysis our study proposes an approach for identifying ED-prone people, the use of which reveals the current situation with regard to EDs in China. The identified ED-prone people were all willing to share information about diet, body shape and slimming while reporting their disease condition. Most of these users were young females, who were active on social media but in a negative frame of mind. With the method proposed in this study, it is possible to identify individuals with an ED and carry out timely intervention via social media at a very low cost.