How do people define their online relationships? Do “friends” still offer social support to each other on Facebook? This article discusses the effects of tie strength and gender difference on social support for online friendships. The results showed that individuals with strong ties have a significantly higher frequency of clicking “like,” and posting comments and messages on Facebook than individuals with weak ties do. In addition, females have a significantly higher frequency of liking, commenting and messaging than males. The results reconfirm the gender difference of social support in sociology and reveal the pattern behind user behavior on a social network website. These findings could be applied to the value proposition and to the design of interaction tools of social network websites in the future.