OBJECTIVE： To discuss the countermeasure on the quality improvement of the drug clinical trials in our hospital based on the discovery of key links of the quality of clinical trials. METHODS： Quality results of 14 drug clinical trials in 10 majors from the drug clinical trial institute in our hospital in 2014 were investigated. Referring to the grading and classifying methods of the inspection problems in European Medicines Agency， the key links of occurring problems were analyzed， and the effects of interventions for key links were evaluated. RESULTS： In 2014， totally 125 important and general problems were found， in which， the numbers of problems occurred in case report form filling， informed consent of subjects， enrolling and screening of subjects， investigational products management accounted for 79.20％. The above 4 links were the key links affecting quality of drug clinical trials. According to strengthening the training about relevant knowledge of the researchers， improving system and standard operation procedures management， enhancing link quality control， introducing project clinical research coordinator， developing centralized drug management and other interventions， the total numbers of found important and general problems in 2015 and 2016 were 68 and 59， respectively. Compared with 2014， the differences were statistically significant （P＜0.05）. The numbers of found important problems in 2015 and 2016 were 7 and 4， respectively. Compared with 2014 （4 important problems）， the differences were not statistically significant （P＞0.05）. There were no severe problems during 2014-2016. After interventions， numbers of occurring problems in majors with less complex drug clinical trial had obviously declined in 2016. Compared with 2014， the differences were statistically significant （P＜0.05）. While the major with relatively high complexity of drug clinical trial had no obvious decline in 2016. Compared with 2014， the differences were not statistically significant （P＞0.05）. CONCLUSIONS： Controlling the key links in drug clinical trial process can obviously reduce the occurrence of general problems while has little effect on the occurrence of important problems. It is different for different majors in undertaking drug clinical trial projects， so as the links and degree of occurring problems. It should be distinguished in quality control checking.