This paper selects five discussions by Fang Yizhi on Mencius's theory of human nature to reveal his unique understanding through interpretation:(1 )He categorizes"the mixture of good and evil in human nature"and"the three grades of human nature"into the same type.(2)Fang interprets Mencius's discourse on the unity of"mind""nature"and"heaven"not from the standpoint of intellectual reason,but from moral reason.(3)He explains Mencius's concept of the unity of"nourishing qi"and"practicing form"using the idea of"transcending existence and non-existence",highlighting a strong speculative philosophical aspect in his interpretation.(4)Fang defines humans'spontaneous learning ability as"habitual nature"or"unique nature"and traces"unique nature"back to"universal nature".Since"universal nature"exists before the formation of the universe (logically prior),tracing"unique nature"back to"universal nature"implies that humans are born with a spontaneous learning ability.Fang's definition of inherent human characteristics based on this spontaneous learning ability is markedly different from Mencius's emphasis on defining human characteristics through moral consciousness and moral capability.