With the population of social networking services (SNS) like WeChat, they have emerged as an increasingly important media or platform that facilitates product-focused electronic word-of-mouth (eWOM) activities. Meanwhile, e-commerce has become an essential part of our daily life. The goal of the current research is to discover the key factors that affect consumers’ willingness to engage in eWOM behaviors on mobile social media like WeChat. We mainly investigate eight factors including personal factors, WeChat usage, social communication, e-commerce participation, consumer online perceptions, perceived risk, platform factors, and product factors, which may encourage or restrain consumers to spread eWOM on WeChat. We have constructed a theoretic model and proposed a series of hypotheses. In order to verify the model as well as the hypotheses, we have carried out a questionnaire survey. Moreover, we use SPSS 20 software to analyze the results of the survey. We try to find out the significant factors that affect eWOM most on WeChat. According to the result, social communications and consumer online perceptions have shown strong influence on eWOM. Finally we make a discussion on the results, which could be used to support the marketing or sales activities of potential enterprises.