Lu Xun situated himself at the crossroads of agricultural tradition and modernist inception during the tumultuous Republican period. As a result, fraught with his affection towards his origins and aiming to register his modernist sensibilities, he widely scattered various animals throughout his fiction and essays. However, more scholarly attention should be paid to the theoretical interpretations of these nonhuman historical and affective agencies and they deserve to be regarded as unique references to the social and political representations of the Republican era. This paper analyzes how Lu Xun represents animal images and discusses the relationship between animality and humanity in his writings. Employing eco-criticism and Foucauldian bio-politics, I argue that the animalistic reading of “A Madman’s Diary” contrasts with the conventional cannibalistic reading and marks a revolutionary beginning to Lu Xun’s concern towards animality and humanity. Later echoing with the social Darwinism popular at the time, Lu Xun invests more nuanced affects in three different categories of animals through which he contemplates domestication, vulnerability, and self-definition. Finally, I argue that by inventing a discourse of animality and humanity, Lu Xun casts his pioneering gaze on Chinese morality, modern subjectivity, and the natural environment.