In order to deeply explore the factors that affect the occurrence of illegal events in drug clinical trials, this study uses grounded theory as the research method to sort out and analyze the illegal records of drug clinical trials in a large general hospital in Anhui Province in 2017. By 2019, construct a model for the illegal effects of drug clinical trials. The results show that "pre-control of drug clinical trial risks" and "prerequisite basis for drug clinical trials" have a significant impact on the occurrence of plan violations. It is recommended to improve the research environment and resource conditions, strengthen the relevant training of researchers and research teams, and rationally design research plans. Establish a safety monitoring system, improve the reporting and handling mechanism for adverse events, guide researchers to deepen the transformation of moral concepts, and provide some ideas and suggestions for reducing the occurrence of illegal events in clinical trials and controlling the quality of drug clinical trials.