The thesis is to study the relationship between corporate governance and cost of debt, and to analyze whether corporate governance affects the rating. To analyze the relationship between cost of debt and corporate governance, we find that the proportion of cash flow rights held by controlling shareholders and disclosure level are significant negatively correlated with the cost of debt. In additions, the result of the relationship between rating and corporate governance indicates that the proportion of cash flow rights held by controlling shareholders, the proportion of board seats held by independent directors and supervisors, the board size and disclosure level are all significant negatively correlated with the rating. The proportion of board seat held by controlling shareholders is significant negatively correlated with the rating, but is not at anticipated direction.