Abstract: This paper probes into the real-learning thought in Cheng Hao and Cheng Yi's rationalism system. In ontology, Cheng brothers' real-reason is different to Buddhism and Taoist school's empty noumena. In the theory of Gongfu, Cheng brothers maintained the real cultivation of Gongfu, the genuine knowledge of reason through personal investigation of things and practice, and participation in the real affairs of managing state. Cheng brothers thought that study of Confucian classics was close to the original meanings, and Cheng Yi said that study of Confucian classics was real-learning. They affirmed people's basic passion, desire and interest, advocated simple and unadorned style of study. Cheng brothers' thought of real learning is the source of real-learning of the Ming and Qing Dynasties.