随着国民经济的发展，我国的债券市场规模不断壮大。在债券市场迅速发展的同时，债券的违约风险日益显现。自2014年“11超日债”违约事件发生打破刚性兑付以来，债券市场违约事件频发，尤其是大型高评级国有企业的违约，给债券市场造成了较大冲击。本文以AAA评级债券——永煤控股债券违约为案例，详实分析大型国有企业债券违约的外部原因和内部原因，在此基础上给出防范化解债券风险的建议。

首先，本文分析了文章的研究背景和研究意义，介绍了信用债券、隐性担保和刚性兑付、债券违约等与文章相关的基本概念，总结了债券违约影响因素的理论基础，这具体包括经济周期理论、信息不对称理论、风险与收益相匹配理论以及非正式制度理论，梳理了永煤控股集团的基本情况、发展历程、经营业务和股权结构以及永煤控股债券违约的基本情况、具体过程以及违约后各主体采取的相关措施。

其次，本文概括分析了永煤债券违约的外部原因，发现煤炭行业低迷、债券中介机构未充分发挥其应有的作用、债券投资者秉持的国企信仰等加剧了永煤债券违约的风险，是导致其违约的主要外部原因。再者，本文详实分析了永煤控股债券违约的内部原因，主要从财务因素和非财务因素两个角度进行总结。财务因素方面具体包括公司的盈利能力下降、偿债压力加剧、货币资金不足等，非财务因素方面具体包括公司的经营战略不佳、融资风险较高、关联方占用资金以及母公司救助能力弱等。

最后，本文进行了总结，并在发债企业、中介机构、政府和投资者等四个角度给出了防范化解风险的建议。发债企业要优化债务期限结构、完善内部治理、提高资源配置效率。中介机构要切实履行其责任，特别地，信用评级机构要强化自身声誉约束，充分发挥债券市场“看门人”的作用；承销商要严格尽职调查；审计机构要出具真实有效的审计结果；政府部门要完善信息披露制度、统一监管标准、加大监管力度；债券投资者要增加风险识别能力、破除刚性兑付和国企信仰。

With the development of national economy, the scale of bond market has been growing steadily. With the rapid development of bond market, the risk of bond default appears day by day. Since the "11 Chaori bonds" default event broke the rigid payment in 2014, the bond market defaults frequently, especially the defaults of large high-grade state-owned enterprises, which caused a great impact on the bond market. In this paper, we use the AAA rated bond Yongmei Holding default as a case to study the large state-owned enterprise bond default of the external and internal reasons in detail and provide suggestions to prevent and resolve the bond risk defuse risks.

First of all, this paper analyzes the research background and research significance, introduces the basic concepts related to this paper, such as credit bonds, implicit guarantee and rigid payment, bond default, and summarizes the theoretical basis of factors affecting bond default, including the economic cycle theory, information asymmetry theory, risk and return matching theory and informal system theory. This paper has sorted out the basic situation, development history, business and equity structure of Yongmei Holding Group, as well as the basic situation and specific process of bond default of Yongmei Holding Group and the relevant measures taken by each subject after default.

 Secondly, this paper summarizes the external reasons for the default of Yongmei bonds, and finds that the downturn of the coal industry, the lack of bond intermediaries to give full play to their due role, and the belief of bond investors in state-owned enterprises aggravate the risk of default of Yongmei bonds and are the main external reasons leading to the default of Yongmei bonds. Furthermore, this paper summarizes the internal reasons for the bond default of Yongmei Holdings from the perspective of financial factors and non-financial factors. Financial factors include the company's declining profitability, increasing debt repayment pressure, insufficient monetary funds, etc., while non-financial factors include the company's poor business strategy, high financing risk, funds occupied by related parties, and weak rescue ability of the parent company.

inally, this paper summarizes and gives suggestions on preventing and defusing risks from four perspectives: issuing enterprises, intermediaries, governments and investors. Enterprises issuing bonds should optimize the maturity structure of debt, improve internal governance, and increase the efficiency of resource allocation. In particular, credit rating agencies should strengthen their own reputation constraints and give full play to the role of "gatekeeper" of the bond market. Underwriters should conduct strict due diligence; Audit institutions shall produce true and effective audit results; The government departments should improve the information disclosure system, unify the supervision standards, and strengthen the supervision. Bond investors should increase the ability to identify risks, break the rigid payment and state-owned enterprise belief.