With great growth of the use of internet ,the communication based on computer-mediated system or so called electronic word-of-mouth becomes more important. In these ways to exchange information, forward mail is unique and powerful especially. In this research, we would like to know what factors make people to decide to forward a e-mail or not, and what kind of roles these factors play in the process to make decision. Three factors were discussed in this research, including¡Gmessage framing, source credibility and product involvement, and the theory of reasoned action was applied to explain the behavior of forwarding e-mail. Through ANOVA and regression analysis to analyze 472 effective samples, the findings are outlined below¡G 1. E-mail users hold better attitude to forward negative message, and have more intention to forward it. 2. E-mail users hold better attitude to forward the message which has high source credibility, and have more intention to forward it. 3. The effect of subjective norm on intention to forward the email is greater than the effect of attitude.