2021年以来，随着“碳中和”概念的兴起，国内绿色债券迎来了新一轮的发展阶段。自2016年起，我国绿色债券市场从无到有，逐渐发展成为支持环境保护和可持续发展的重要金融工具。绿色债券在发行定价时是否具备成本优势，也成为业界和学界普遍关注的问题。本文聚焦研究中国绿色债券一级市场，构建以债券发行时信用利差作为被解释变量的回归模型，通过实证分析的方法探究绿色债券相较于普通债券是否具备成本优势。全样本的回归结果表明，在控制其他因素的条件下，绿色债券在发行时并未享受到更低的发行利差，反而表现出约8.4个基点的成本劣势，即“绿色溢价”不存在。进一步地，基于金融债和非金融债在债券特征、资金使用方式以及监管力度方面的差异，将样本分为金融债组和非金融债组两个子样本分别进行回归。结果表明，绿色溢价在金融债券组中是显著存在的。对于这一结果，本文提出了流动性差异以及因信息不对称因素导致的风险溢价两方面的原因并加以说明。此外，本文对央行于2018年中颁布的一项绿色债券相关的政策进行了效果分析。通过将符合条件的金融债于政策时点前后进行分组回归，本文发现，该政策显著提升了绿色金融债的绿色溢价，绿色金融债相较于普通金融债券的成本优势在政策实施后得到了增强。最后，本文基于信息不对称程度的视角，探究信息不对称程度的降低是否有助于提高绿色债券的绿色溢价。对此，引入了外部认证和发行连续性两个代理变量加以验证。实证分析表明，信息不对称程度的降低确实可以提高绿色债券发行时的成本优势。这一结果也从另一角度说明了中国债券市场上不存在绿色溢价的原因之一，在于投资人和发行人之间的信息隔阂与不信任。基于这些讨论，本文在最后给出了绿色债券发展的相关政策建议。

With the rise of the concept of "Carbon Neutrality" in 2021, China’s green bond market has ushered in a new round of development. Since 2016, China’s green bond market has grown out of nothing and has gradually developed into an important financial tool supporting environmental protection and sustainable development. The question of whether green bonds have a cost advantage in the primary market is of great concern to both issuers and investors.This article focuses on the primary market for green bonds in China. By constructing a regression model with credit spread at issuance as the explained variable, this article explores whether green bonds have cost advantages compared to conventional bonds through empirical analysis. The regression results of the full sample show that under the control of other factors, green bonds do not have a lower issuance spread at the time of issuance, but show a cost disadvantage of about 8.4 basis points, that is, there is no “green premium” in China’s bond market.Furthermore, based on the differences in bond characteristics, use of proceeds and degree of supervision between financial bonds and non-financial bonds, the sample is divided into two sub-samples for regression. The results show that the green premium exists significantly in the financial bonds group. Regarding this result, this article puts forward two reasons—the difference in liquidity and the risk premium caused by information asymmetry.In addition, this article analyzes the effects of a green bond-related policy issued by the People's Bank of China in mid-2018. By grouping eligible financial bonds before and after the policy point, this paper finds that the policy has significantly increased the green premium of green financial bonds. The cost advantage of green financial bonds compared with ordinary financial bonds has been enhanced ever since.Finally, based on the perspective of information asymmetry, this article explores whether the reduction of the degree of information asymmetry can help increase the green premium of green bonds. In this regard, two proxy variables, external certification and issuance continuity, are introduced to verify. Empirical analysis shows that the reduction of information asymmetry can indeed increase the cost advantage of green bond issuance. This result also explains in disguise that one of the reasons why there is no green premium in the Chinese overall bond market is the information gap and mistrust between investors and issuers. Based on these discussions, this article finally gives relevant policy implications for the development of green bonds.