With the rapid development of cyber economy, Word-of-Mouth has an increasing important influence on consumers' purchase decisions. As WOM is a consumer-dominated channel of information, its senders and receivers are thought to be independent of marketers. This paper selected 192 consumers who had experiences on online purchase as research object. Then it researched consumers' self-confidence, perceived risk, WOM actively sought and discussed the relationships between these factors and influence of WOM. The results show that consumers' self-confidence has a direct and positive effect on WOM actively sought. And perceived risk has a direct and positive effect on actively sought. Lastly, WOM actively sought has a direct and positive effect on influence of WOM. From the above conclusions, it is known that WOM actively sought is the key mediator in affecting influence of WOM.