Abstract: Abstract: Industrial cluster which is helpful to the cluster firm innovation has been an important competitive advantage theory reflected in the cluster literature. From the perspective of core firms, industrial cluster theory is re-studied here. It is found that the cluster factors still have a positive effect on the core firm innovation during the period of core firm, but its influence has relatively been weak, and its function mechanism has changed from the direct way to the indirect one, Therefore, the scale growth of the core firm essentially has a mediator effect on the core firm innovation. Actually it means, with the development of core firms, the division of labor and location of cluster firm have been clearer, so the mode of cluster innovation supported by the core firm has been changed correspondingly, the core firm has increasingly taken the innovation task as an engine, the innovation subject has also returned to the firm individual level from the whole cluster level, especially for the special core firm, that means it is very difficult for the cluster innovation theory emphasizing on the whole level to maintain its original meaning to a certain degree.

Key words: cluster, core firm, technical innovation, mediator effect