Abstract: OBJECTIVE To continuously improve of the quality of drug clinical trials by quality control circle(QCC). METHODS Continuous improvement of the quality of drug clinical trials was chosen as the subject. By using the method of QCC, summary and collection quality control reports and protocol violation forms to analyze the main causes leading to the quality defects of drug clinical trials. It was formulated and implemented countermeasures, evaluated tangible and intangible achievements. RESULTS After the QCC activities, the number of defects in drug clinical trials in the Affiliated Drum Tower Hospital of Nanjing University Medical School decreased from 91 to 43, the improvement rate was 52.75%, the target rate was 106.67%, the ability of the crews to solve problems and to coordinate had been significantly improved, and the management of drug clinical trials was more standardized. CONCLUSION The QCC activities are helpful to continuing improve the quality of drug clinical trials and continuously improve the management level of drug clinical trials.