Around the time when Nanking was occupied by the enemy in December in 1937，Nanking Massacre made by the Japanese army amazed the whole world，which was a disaster for the Nanking people. The massacre was an unforgettable memory of the pain for the survivors. In the early postwar period，with the investigation into the atrocity of the Japanese army in Nanking and the trial on the Japanese war criminals，the issue of Nanking Massacre was widely known，and the collective memory formed initially. From the fifties of the 20^th century，the historical memory of Nanking Massacre went through several phases：the urban memory，the national memory and the human memory，and each phase showed different forms and traits，which reflected the deepening of the understanding of Nanking Massacre. As memory of the world，the deepening historical cognition and the essential understanding，comply with the trend of the times and the wish of the international community about the world peace.