Objective To investigate the mastery degree of GCP (Good Clinical Practice) in Guang’anmen Hospital of China Academy of Chinese Medical Sciences (hereinafter referred to as“Guang’anmen Hospital”). Methods Totally 338 clinical researchers, covering 18 clinical professional sections and medical clinical trial institutions, in Guang’anmen Hospital with both qualification of clinical trials and GCP certificate were investigated in 23th-27th June 2014. The investigation was in the written answer sheet form, including four noun explanations and 36 multiple choice questions, which were related to GCP. Results 338 researchers could accurately explain the concepts of 4 nouns, and 57 (16.86%) researchers could do all multiple choice questions correctly. 141 (41.72%) researchers chose 1 wrong answer and 89 (26.33%) researchers chose 2 wrong answers. 39 (11.54%) researchers failed to answer 3-4 questions. Only 12 (3.55%) researchers failed to answer 5 or more questions. Conclusion The mastery degree of clinical researchers with qualification of clinical trials and GCP certificate in Guang’anmen Hospital is satisfied. In the future, pertinence and diverse training should be strengthened, in order to improve the overall level of the mastery degree of GCP.