The Flexner Report published in 1910 was a landmark report in the history of the development of medical education in the United States.Academic circles generally believe that the Carnegie Association for the Advancement of Teaching commissioned Flexner to investigate American medical education.Then the Flexner Report established the development direction of American medical education,promoted its reform to modernization,enabled it to catch up from behind,and became the world's medical education center in the 20th century.However,a re-examination of historical data revealed that the Carnegie Association for the Advancement of Teaching was not the original cause of the Flexner Report,and the reform of American medical education in the early 20th century was not the result of a single factor,but the outcome of a combination of forces.To this end,this article will try to discuss the true origin of the report and the pathway and origin behind its impact on American medical education.