In the academic community of Mencius research, the question whether Mencius' thought on character education includes the element of subjective spirit is very controversial. Some scholars believe that Mencius was only a thinker who lived in the absolute monarchy. So, Mencius actually did not have the consciousness of democracy and subjective spirit. He was a thinker ruled by the absolute monarchy and emperor, and his academic idea was also controlled by the absolute monarchy and emperor. In a word, Mencius did not have the democratic idea or subjective spirit in his life, neither in his books. However, other scholars believe that Mencius' idea about political construction and character education involved profound concepts of humanism and human-based thought. Although Mencius was not a democratic, but he advocated the respect for human nature and personal dignity in the framework of Confucianism. Therefore, there existed subjective spirit in Mencius' thought on character education. But, what's the essence of Mencius' idea? Did Mencius advocate moral subjectivity or not? This paper begins with this controversial question. Using the methodologies of text interpretation and historical analysis, it analyzes the masterpiece Mencius and its academic ideas. Based on the comprehensive analysis of the classical book and impressive ideas, the author argues that Mencius' thought on character education focused on subjectivity, which advanced the Pre-Qin Confucianism's humanitarian spirit to a new height. We can look at the great contributions of Mencius and his ideas from four aspects. First, Mencius thought that everyone had natural morality and natural moral ability to be a subjective moral personality. And, everyone can be a subjective moral personality. His theory of human nature transcends Confucius', which is unclear. Second, in terms of the methods of self-cultivation, Mencius put emphasis not only on Confucius' idea about self-reflection, but on the self-cultivation of moral courage and sense of justice. Third, in terms of the moral will, Mencius emphasized the cultivation of strong moral will through daily life and moral life. His idea is more profound and systematic than Confucius'. Fourth, Mencius not only advocated the moral action of gentleman (Jun Zi), but also the real man personality, which can defend the social morality and justice. In a word, Mencius's thought on character education was beyond the limit of his time and space. It involves abundant sprit of subjectivity, which deserves more exploration.