With the advance of information technology and the advent of the Internet epoch, the form of discourse has become diversified, which leads us to consider its new approaches and perspectives. This paper, by adopting the main points of systemic functional linguistics of Halliday, analyzes the choice of semiotic modes and meaning integration in multimodal blog webpages, focusing on the role of choice of semiotic modes in expressing the three metafunctions of language with reference to the theory of systemic functional linguistics. On the basis of the analysis, a dynamic model of HumanComputerHuman Interaction (HCHI) is proposed, about which the previous studies have seldom attempted.