In the era of digital economy，digital transformation has become an inevitable trajectory of enterprise development. From a supply chain perspective，the costumer digital transformation can exert substantial influences on supplier through supply chain channels. However，does the digital transformation of costumer affect the digital technological innovation of supplier? To address this question，this paper established an econometric model by matching the data among listed company on China' Shanghai and Shenzhen A-share market from 2011 to 2022. It empirically examined the spillover effects of costumer' digital transformation on supplier' digital technological innovation and its underlying mechanisms. The results indicated： （1） The digital transformation of costumer exerts a positive spillover effect on the digital technological innovation of supplier，a series of robustness tests and endogeneity discussions confirm the reliability of this conclusion；（2） The impact of customer companies' digital transformation on supplier companies' digital technological innovation is stronger when： the supplier and customer companies operate in the same industry，or the supplier companies' industry exhibits a high level of digital transformation；（3） the customer companies' digital transformation promotes supplier companies' digital technology innovation through two channels： information spillovers and supply-demand alignment. The intensity of cooperation and industry competition strength positively moderate these relationships. This study revealed the underlying mechanism of customer companies' digital transformation influencing supplier companies' digital technology innovation from a supply chain perspective，enriching the economic consequences of corporate digital transformation and providing theoretical support and decision-making references for advancing corporate digital technology innovation practices；（2） this effect is more pronounced when supplier and customer operate within the same industry or when supplier is located in highly digitized sectors；and （3） the customer digital transformation enhances supplier innovation through information spillovers and improved supply-demand alignment，with cooperative intensity and industry competition positively moderating these mechanisms. Overall，this study has elucidated the mechanisms through which customer digital transformation influences supplier digital technological innovation from a supply chain perspective. It has extended the literature on the economic consequences of enterprise digital transformation and will provide theoretical insights and policy implications for fostering digital technological innovation.