The supply chain is a core channel for inducing knowledge spillover effects among companies, but studies onthe micro-mechanism of knowledge spillover along supply chain of green technology innovations are scarce. From the perspective of supply chain relationship, this paper systematically examines the impact of manufacturing customer companies’ green technology innovations on supplier companies in both “quantity” and “quality” dimensions, and further reveals the chain reaction in supplier company performance. This study finds that customer companies’ green technology innovations help improve green innovations by supplier companies both qualitatively and quantitatively. The heterogeneity analysis shows that supply chain spillover effects of green technology innovations are more pronounced in case of higher customer concentration, non-state-owned enterprises, or southern regions. Further investigations reveal that customer companies’green technology innovations also have spillover effects on supplier companies’future economic and environmental performance. This paper sheds new light on the implicit contribution of supply chain spillover effects in green technology innovations amongst Chinese manufacturing companies, which has theoretical and practical significance for the transformation and upgrading of Chinese manufacturing industries and for smoothing the domestic circulation.