The difference between Taoist apriorism and Legalist experimentalism as to human nature lies in that Taoists seek after the reality of humanity, thus establishing the true-false theory of human nature, while Legalists seek after the advantage of humanity, therefore developing the advantageous-disadvantageous theory. Their different pursuits lead to the different realms of human nature: Taoists’natural realm of humanity and Legalists’utilitarian one. Besides, their realization of the realm is also different from each other in that Taoists realize theirs in a negative way while Legalists in a positive one. In short, it is of great significance to study the difference between Taoist and Legalist theory of humanity and the different dimensions of the theories as to human nature in pre-Qin period. In addition, it will surely deepen the research in modern human science.