A question has long puzzled automobile components firms is that whether the automakers is the important knowledge source for their innovations? Previous empirical studies, which were designed in the macro level, gave the overview scene. The main purpose of this paper is, from the micro view, to clarify for automobile components suppliers about the real effect of using automakers’ knowledge in their innovations. We believe the effect may be different in different contexts. Two dimensions are identified to classify the context: the supplier’s capability in creation and the radicalness of the innovation. Four type contexts of innovations are identified by integrating these 2 dimensions. Employing parts suppliers in the United States as the research subject, and applying patent data to construct variables, we examine the effects of using automakers’ knowledge in different contexts. The result shows that, the automakers' knowledge play the major role in the case of a weak supplier initiates a less radical innovation. Further, when a strong supplier initiates an innovation with high level of radical, using more automakers’ knowledge will decrease his innovation quality. The result also shows that, strong suppliers can’t gain benefits by using automakers’ knowledge, what they should do is searching knowledge broadly from other external sources.