In recent years, with its amazing online interactive promotion ability, live marketing has attracted the attention of theoretical scholars and practical experts. This study takes “co-presence (CP)” and “social presence (SP)” ,which are the prominent features of live marketing, as the breakthrough point to explore the mechanism of the influence of social presence and social presence on herd consumption. In this study, consumers with live broadcast watching experience are taken as participants, and the method of structural equation modeling is used. It is found that: in the web live broadcast situation, the sense of co-presence has a significant positive impact on the herd consumption behavior. The promotion effect of social presence on herd consumption is partially mediated by trust in user-generated information (TUGI), and the promotion effect of social presence on herd consumption is completely mediated by trust in user-generated information. The mediating effect of the two kinds of presence (SP, CP) on herd consumption through the trust in user-generated information is regulated by tie strength between buyer and network-anchor (TSBBN).