Through Web-based consumer opinion platforms, the Internet enables customers to share their opinions on, and experiences with, goods and services with a multitude of other consumers; that is, to engage in electronic word ofmouth (e-WOM) communication. We think that e-WOM can be decomposed into four factors: the communicator (sender), the stimulus (message), the receiver, and the response. The role of the four key elements path constitutes the difference of e-WOM and WOM. This effect path is different according to the different e-commerce mode: Share Comments Model, Opinion Leaders Model, Group-buying Model. Completely Free of Charge, Promotion Strategies, Cooperation with Banks, and the three strategies is the key factor of the e-WOM. Credit rating of Taobao solves the problem of quality and sufficiency of the information. They have feedback mechanism to let buyers evaluate the e-WOM after reading it.