Compared with the research on consumer engagement in brand community, the research on consumer engagement in brand public has been relatively less. This research aimed at exploring how brand public characteristics such as information variety, various communications and no limitation in expressing self affect the brand public engagement. 274 questionnaires answered by Chinese consumers are used to conduct analysis. Principal component analysis is used to test the reliability and validity of each construct, and structural equation model is used to test hypotheses. The study finds the positive effects of information variety on information benefits, those of various communications on social benefits, and also positive roles of no limitation in expressing self to brand-related self-expression motivation. And each of the information benefits, social benefits and brand-related self-expression motivation is proved to positively affect brand public engagement. The study implies that marketers should give attention to characteristics of brand public, and provide the ways by which members of brand public engage the brand. Additionally, marketers should pay more attention to both direct and indirect engagement activities of consumers toward brand public in social media to better understand their target consumers.