Innovation cluster of producer services industry emerges in the world, in which the firms cooperate widely. The meaning of producer services industry is reviewed, and the definition of innovation cluster of producer services industry is given. It finds that the interfirm relationship in innovation cluster of producer services industry has a structure of Synergism Network, which is analyzed from dimensionalities of mode of governance, power dependence, relationship complexity, relationship importance and relationship change. Then a model of Synergism Network of interfirm relationship in innovation cluster Of producer services industry is constructed.