<p>This paper examines green-bond issuance from two perspectives: the marketization of green finance and the application of government policies. Using Chinese provincial-level panel data (2007–2021), we apply a two-way fixed-effects model, a continuous difference-in-differences model, a mediation-effects framework, and Qualitative Comparative Analysis to systematically evaluate the carbon-reducing effect of green bond issuance and to test whether low-carbon pilot policies amplify this effect. The results show that green-bond issuance significantly lowers regional carbon intensity; the reduction is more pronounced in sparsely populated provinces, in regions with higher financial development, and among privately owned enterprises. Mechanism analysis reveals that green-bond issuance reduces carbon intensity through two mediated channels: green-technology innovation and industrial-structure upgrading. The mediation effect via green-technology innovation is further moderated by financing cost. Additional analysis demonstrates that the nationwide implementation of low-carbon pilot policies markedly stimulates green-bond issuance and thereby strengthens the carbon-reduction effect. Our findings corroborate the role of green bonds, a vital green-finance instrument, in reconciling economic growth with environmental protection, and this paper provides both empirical and theoretical support for implementing the green and low-carbon development strategy and for deepening the green-finance reform.</p>