Abstract: From the perspective of enterprise business relationship network, this Paper discusses the influence of customer relationship to R&D investment intensity. The results show that the relationship between customer concentration and R&D investment takes on an inverted-U shape. Further, we explore the effect of business group affiliation and local financial development on the relationship between customer concentration and R&D investment. We find that this inverted-U shape still exists in non-group-affiliated firms, but the relationship between customer concentration and R&D investment takes on negative correlation in group-affiliated firms. Similarly, this inverted-U shape still exists in regions with developed financial development, but the relationship takes on negative correlation in regions with less developed financial development. Our study shows that enterprise’s R&D investment as a kind of specific asset investment, not only demonstrates the value of its signaling in terms of customer concentration, but also relects different intensity in different financing constraints scenarios, highlighting its significant moderating effect, this paper helps enterprises consider R&D investment decisions from multiple perspectives.