Abstract:    With the trend towards industry concentration and strengthening of the dominant position of top enterprises in the supply chain, the phenomenon of key customer-supplier duality in the supply chain management practice is becoming increasingly common. However, with the outbreak of the "Amethystum" incident, whether key customer-supplier duality can empower enterprises to develop with high quality has become a focus of academic discussion. This paper selected A-share listed companies from 2007 to 2022 as the research object, and used a combination of panel fixed effects model and quasi-natural experiments to study the impact of key customer-supplier duality on the innovation efficiency of node enterprises. It was found that: firstly, key customer-supplier duality has a negative impact on the innovation efficiency of enterprises; secondly, the mechanism is manifested as increasing corporate financing constraints and reducing supply chain efficiency; thirdly, when a company has strong absorption capacity, effective internal control, low dependence on the supply chain, and its key customers/suppliers are state-owned enterprises, the negative impact of key customer-supplier duality on the corporate innovation efficiency can be effectively alleviated. This paper has incorporated suppliers and customers into a unified research framework, focusing on the impact of supply chain relationships on enterprise innovation from a more comprehensive perspective and enriched existing literature, and it will provide reference for strengthening the supervision of key customer-supplier duality behavior in management practice, suppressing opportunistic behavior, and empowering high-quality development of enterprises.

Key words: key customer-supplier duality, enterprise innovation efficiency, financing constraint, supply chain efficiency