Taking the pilot reform of tax-related government functions as a quasi-natural experiment, this paper uses the data of A-share listed companies from 2011 to 2022 and constructs a multi-period DID model to examine the impact of taxation business environment optimization on supply-chain transparency. The results show that the optimization of the taxation business environment significantly improves supply-chain transparency. This effect is more obvious in enterprises with higher specialization costs, those with higher supply-chain concentration, and those in regions with lower intensity of tax administration. Mechanism testing shows that the optimization of the taxation business environment improves supply-chain transparency by suppressing agency motives of the management, reducing uncertainty in business activities, strengthening penalties for tax-related violations, and sharing credit information. Further research finds that the optimization of the taxation business environment has a more significant promoting effect on the transparency of enterprise suppliers than customers. Economic consequence testing shows that the optimization of the taxation business environment significantly enhances corporate value, social responsibility performance, and supply-chain stability by improving supply-chain transparency. This paper provides a positive reference from the perspective of tax governance for improving supply-chain transparency.