OBJECTIVE： To study the influencing factors of protocol deviation in drug clinical trial implementation， and provide reference for improving the quality of drug clinical trial. METHODS： Quality verification was conducted for the drug clinical trial projects in the First Affiliated Hospital of Chongqing Medical University during 2010-2016， and protocol deviations in each year were retrospectively studied， classified and analyzed. Category， frequency， international and domestic pilot projects and the differences of protocol deviation after full-time research nurse participating in trail management were explored， and the measures were put forward. RESULTS： 27 drug clinical trials were implemented in our hospital during 2010-2016， including 949 cases， 176 cases with protocol deviation， accounting for 18.55％. Deviation protocol in drug clinical trial was decreased year by year for 7 years. The categories were mainly incompleteness of observation/records （30.11％）， checking omission/“broaden the window” （28.41％）， adverse drug events and improper combined medication （14.20％） and omission in drug management （11.93％）. The proportion of protocol deviation with full-time research nurse participated was lower than the projects without full-time research nurse （11.11％ vs. 28.67％， P＜0.01）， and proportion of deviation protocol in international multi-center project was lower than the domestic projects （6.60％ vs. 28.84％， P＜0.01）. CONCLUSIONS： It is suggested to pointedly strengthen the weak links of drug clinical trial. For example， clinical trial institutions should establish the clinical trial data retention system， electronic data should be timely backed up in a different places， etc. Besides， clinical trial institutions should equip professional full-time research nurses as much as possible， learn the rigorous scientific experimental design， standard operational procedures and the authenticity of data processing from the international multi-center clinical trial projects to effectively reduce the incidence of deviation protocol and improve the quality of drug clinical trials.