This paper incorporates customer digital transformation behavior decisionmaking into the research framework of enterprise inefficient investment, and uses the data of the top five customers disclosed by Ashare listed companies in Shenzhen and Shanghai from 2007 to 2019 to test the following findings: customer digital transformation has a positive spillover effect on enterprise inefficient investment, and this positive spillover effect is mainly reflected in inhibiting enterprise overinvestment. This conclusion still exists after a series of robustness. Further research finds that information coordination and executive governance are two channels for customer digital transformation to improve coordination inefficient investment, which confirms the existence of coordination governance effect of digital spillover. In addition, when the nature of the relationship between customers and enterprises is better, the digital divide between customers and enterprises is larger, and the financing constraints of enterprises are higher, the improvement effect of customer digital transformation on enterprise inefficient investment is better. This paper not only affirms that digital spillover caused by customer digital transformation can improve enterprise inefficient investment, but also provides a solution for alleviating the contradiction between supply and demand among enterprises. Moreover, the coordination governance effect of supply chain digital spillover is found and verified, which deepens the academic understanding of supply chain digital spillover from all walks of life. All in all, this paper has practical significance and theoretical value.