Abstract: To alter non-ration's abnormal position as is losing in the construction of public policy and promote the return of the position,the article is based on the seeking the reason, and probes into the possibility of the non-ration's inevitable entry in the process of making policy and the return of its necessary position mainly from two angles of the theory of knowledge and the theory of human nature.In accordance with Similar Classification Epoch named by scholar in post-modem when the construction of the harmonious public policy is, the article puts forward the necessary research and practice of a new thinking.The seeking will further corrects abnormal inclination which attaches too much importance to ration and too little to non-ration in the construction of harmonious public policy,improving and broadening the thinking ground on which the harmonious public policy builds.