The mechanism of business model innovation has drawn more and more attention by the firms and scholars all over the world. However, it has been never reached an agreement for a long time because of the difference of theoretical perspectives. This article builds a twodimensional framework of innovation mechanism after reviewing previous literatures, which consists of strategic analysis, factorsusing and revenue realization. This article analyzes four practice models about the business model innovation by multicase study method. Our research on systems thinking shows that investment pattern is the key factor to continue business model innovation, and the intrinsic causal relationship between the innovation activities is the immanent mechanism which promotes enterprises to change its business model, and the initial innovation activities are the trigger causes.