I. Introduction
The network media is eliminating the monopoly of traditional media. It is re-defining the information dissemination methods in digital times [1]. In addition, the network media has gradually transformed itself into an important platform for public opinion development of emergency [2]. However, the network media is a combination of multiple forms, such as post bars, forums, teacher and student blogs, and microblogs [3]. Moreover, the internet forum has become an effective tool for emergency public opinion dissemination. Meanwhile, textual information takes a great position in internet forum, especially during emergency.