Abstract: A Madman's Diary by Lu Xun extends the theme of "killing human" in the history of modern literature. The metaphor of "killing human" here is "the feudal ritual's killing", while the theme of "alienation" repeatedly written in the novels of the New Sense School reveals how the urban civilization depresses a healthy humanity. The latter can be regarded as a further account of Lu Xun's "killing human". Both them expose the dissolution of the world of human nature, reflecting the critical meaning of reality and the writer's sense of responsibility and profound thinking in the writing.