The Jinan Massacre on May 3,1928 was an important event in the history of modern Sino-Japanese relations. It was also the first confrontation between the Nanjing national government headed by Chiang Kai Shek and the Japanese authorities in international public opinion. Despite considerable amount of research,due to a neglect of archival historical materials, especially Japanese archives, there are misunderstandings in previous studies. Based on a study of historical archives of China,Japan and the United States,the authors believe that at the beginning of the incident,Japan,with its all-round advantages,mounted a unilateral attack on China in the international public opinion field. After Japan increased its troops in Shandong,international public opinion changed,which placed great pressure on Japan in the financial market. This,to a certain extent,prompted Japan to soften its attitude in the negotiation. China thus gradually began to realize the significance of public opinion and began to use international public opinion to exert pressure on Japan. Throughout the process,though there were bright spots for China, it is generally a failure. Japan through this event tested the effectiveness of its international public opinion processing system,and greatly improved the status of propaganda and public opinion work in the military. The Chinese side, especially Chiang Kai-shek himself, realized the importance of international public opinion. It began to establish a system of uniformity and took the initiative to use international public opinion to exert pressure on Japan in subsequent Sino-Japanese conflicts. In this sense,the Sino-Japanese War of public opinion in Jinan Massacre was a preview of Mukden Incident and Marco Polo Bridge Incident.