在债券市场中，广泛存在着信息不对称情况，债券发行企业与投资者之间就处在信息优劣势两方，这可能会带来债券发行企业道德风险和投资者逆向选择问题，进而影响社会资源合理配置，不利于市场繁荣发展。根据信息传递理论，高质量企业会倾向于向投资者提供更多信息、传递信号来帮助其了解企业真实价值，投资者也回之以积极正面的反馈，实现互利共赢。本文选取2013年1月1日至2015年12月31日的中国企业债券数据，实证研究多重信用评级和信用评级分割情况对债券信用利差的影响，以此观测多重信用评级信息传递效果。

Information asymmetries are widely found in bond markets. For instance, issuing companies have the advantage over the investors, which may cause the moral hazard of issuing companies and inverse selection of the investors. All this will further influence resource allocation, detrimental to a prosperous market. According to the signal transfer theory, qualified enterprises tend to provide more information than low-qualified ones and send signals to the investors to help them understand the real value of the enterprises, while the investors give positive feedback in return. Consequently, mutual benefits and win-win results are achieved. This thesis selects the data of Chinese corporate bonds between January 1, 2013 and December 31, 2015, does an empirical research on the impact of multiple credit rating and credit-rating separation on credit spreads of corporate bonds, and manages to observe and measure the signal transfer effect of multiple credit rating.