With the development of Internet technology, online health forums have become indispensable for people who seek non-professional health support. This research focuses on the content posted by cancer patients and their relatives in online health forums and social networks to raise the following research questions: What is the overall view of the social support network in the online tumor community? What are the information behaviors of the online tumor community in different identities of users? How users interact in this community and build this network of social support? What are the topics users would like to share and talk about? What kinds of users could be the key users in this community? Method: Using the post and comment data of the Oncology Forum of Tianya Hospital in 2019, combined with social network analysis and word co-occurrence network analysis, the following conclusions are obtained: (1) There are some central points in the overall social support network, and there are central users consistent with other social networks. (2) Positive users are more likely to comment on others, and it is easier to get others’ comments, while negative users are more likely to share personal information and do not want to participate more in social interaction. (3) Users focus on posting emotional and emotional content in content sharing. Information-based social support information. The social support experience that this type of information brings to users can be positive and negative. (4) The most active group in the patients’ online health community, followed by the patients’ children. (5) The relationship between users and patients is diverse and there are two types of singularity. Users with diverse relationships are more likely to be commented on, and they are more willing to comment on users who also have diverse relationships.