Credit rating agencies evaluate the firms' value and then give the firms numerical scores. Credit rating agencies try to investigate the source that affects earnings quality. This paper examines the relation of credit ratings and delisting firms in KOSDAQ IPO(initial public offerings). The Korea Exchange(KRX) has strongly imposed a new delisting system called “Substantial Investigation System of Delisting” in February 2009. The purpose of this system is to accomplish 'clean KOSDAQ' with the financial health of the firms and to protect investors with the transparency of accounting. The main hypothesis of this study is that the credit score(SCORE) of t-1(before) IPO year, IPO year, and t+1 (after) IPO year have the negative relation to the delisting. The main test methods used in this study are correlation analysis, two-sample independent t-test, logistic regression analysis. The test sample consists of 572 IPO firms, selected from the Korea Exchange(KRX) listed companies during 2000~2007. The major findings of the study are that the relationship between SCORE and delisting firms at IPO are negatively significant. In this respect, credit grading plays an important role in informing investors of firm's financial conditions from IPO(initial public offerings).