Credit rating is the classification of credit rating agencies according to the results of enterprise credit evaluation. It reflects the level of enterprise credit. Western countries use AAA, AA and A to define the credit rating of enterprises. Others use three types and nine grades, namely 3A, 3B and 3C, to guide investors'behavior by delimiting the enterprise category. Credit evaluation and grading of Chinese enterprises began in the 1980s. Generally, enterprises are classified into three categories. In some places, foreign expressions are adopted, namely AAA, AA and A, while in others, Chinese expressions are used, which are called first, second and third-class enterprises. Different credit grades, enterprises in the market financing, access to bank loans, the degree of difficulty and conditions will vary greatly.