Abstract: Complete Perfect Teaching (“大成圆教”) was a term Mou Zongsan used to describe the “All Holy Completeness” (“大中至正”) of Confucianism, in comparing with Buddhism and Daoism. This term was no longer used by Mou in his later period and thus reflected a paradigmatic transformation of Mou’s thoughts in which he understood the concept of Perfect Teaching differently. Mou first picked this concept from Buddhism and assimilated its core idea into Confucianism, while he was not confined to the discussion on the differences between Buddhism and Confucianism. He developed this concept in the framework of the whole Chinese philosophy. Through Daoist Interpretation of Reason and Metaphysics (《才性与玄理》), Metaphysical Reality of Mind and Nature (《心体与性体》), and Buddha-Nature and Prajna (《佛性与般若》), Mou concluded “undiscriminating speech” from Prajna, “ontological perfection” from the metaphysical reality of nature and Buddha nature, and then established his own system of perfect teaching. In his mature works such as Nineteen Lectures on Chinese Philosophy (《中国哲学十九讲》), Phenomena and Things-In-Themselves (《现象与物自身》), and On Perfect Good (《圆善论》), Mou treated the module of Perfect Teaching as a common module to solve universal philosophical questions. Through the methodology of “purifying oneself respectively, enriching oneself respectively, restricting oneself respectively”, Mou wants to envision a thought system that “appreciating distinct cultural heritages respectively”. From the perspective of Perfect Teaching, we can have a more comprehensive view towards the openness of Mou Zongsan’s philosophy as well as the significance of Contemporary Confucianism.