Abstract: This paper probes into the difference between Cheng Hao and Cheng Yi in their thoughts, and concludes that Cheng Hao stressed virtue in pursuit of the transcendental moral values of life, while Cheng Yi emphasized knowledge so as to grasp the nature of physical phenomena, and their universal principle, namely the law of nature, is that both human beings and the world are characterized with the absoluteness of inherently transcendental morality. The author argues that Chou Tun-Yi,Chang Tsai,Cheng Hao and Hu Hung-s theories of human nature fallinto the category of good-naturedness of human beings, among which Chang Tsai-stheory is characterized with dualism between supreme void and ether. The paper attempts to make a textual research into the authorship of the book CUI YAN, and into the problem concerning the ideas of the other in their respective work.