Internet provides a new channel for people to share information with their friends, includingadvertisements. However, it is not obvious why people share advertisements to their acquaintances online, and what factors play a critical role in affecting advertisements sharing behavior. To find out the answer to the questions, this study uses social capital theory and social cognition theory, and selects the personal motivation dimension, advertising content dimension and advertising source dimension to explore the influencing factors of advertisements sharing behavior among WeChat Moments users. By analyzing the data from the questionnaire survey, we find that knowledge self-efficacy has significant influence on advertisements sharing behavior. Perceived advertisements quality also influence advertisements sharing behavior. The trust among members, the authority of advertising sources and the credibility of media are all the important factors influencing advertisements sharing behavior.