As the three highest interpersonal principles of Confucianism, the three cardinal guides has long been popularly misunderstood as “ruler as the guide of subjects, father as the guide of son, husband as the guide of wife”, especially in the last century. This article aims at correcting this misunderstanding and proves that the three cardinal guides initially refer to “the three kinds of relationships of most importance”, i.e. the relationship between ruler and subject, between father and son, and between husband and wife. Originated from pre-Qin Confucian traditions and interpreted by Dong Zhongshu and Bai Hu Tong, the three cardinal guides had ever been understood in this way for more than one thousand years in Chinese history since the 2rd century BC till the end of 13 century, and some people continued to understand sangang in this way till the beginning of 20th century. The paper argues that Zhu Xi is the most important person who changed the meaning of the three cardinal guides from “the three kinds of relationships” into “the three guides”, but still insisted on its original sense in various occasions. After Zhu Xi, the two meanings of the three cardinal guides showed a very complicated relations in China and the newest meaning as “the three guides” had been popularly seen as the worst part of Confucian tradition as against the modern values of equality and freedom.