Mao Qi-ling (1623-1716) is a famous Confucianist about textual research in early years of Qing dynasty. But his thought was considered to trace back to Yang-ming (1472-1528), even to be an orthodox inheritor by some scholars. Since this argument has not changed the view of Liu Zhong-zhou (1578-1645) was the last but the most important Confucianist in Song and Ming periods, it is necessary to investigate the subject of how did Mao Qi-ling understand Yang-ming’s thought. This paper elaborates Mao’s thought by perusing his works about Daxue, in order to clarify some of the following topics: firstly, Mao traced back to Yang-ming and criticized Zhu Xi (1130-1200) from the standpoint of the unity of knowledge and action. Secondly, how did Mao explain the meaning of the sincerity of the will which was viewed a focal point in Great Learning in his works? I hope to replenish and correct some arguments about the argument of Mao’s “Upholding Yang-ming’s Doctrine, Subverting Zhu Xi’s” nowadays by this paper. In fact, we could find that Mao has not understood the thought of Yang-ming, Zhong-zhou, even Zhu Xi exactly. But this main theme of discussion still offers much information about the feature and the influence of Mao’s thought in that era.