孟子美學的特色，在於他繼承了孔子及孔子之前以「美善合一」為特徵和傾向的儒家美學思想，並且在其性善論的基礎上，將「美善合一」這個命題深刻地體現於主體人格的成全之中。本文首先分別從人的道德情感、道德理性、道德意志三個方面，來看孟子性善論究竟提供了哪些理論基礎，使得「善」與「美」能夠合一在人格的成全之上；再以「可欲之謂善，有諸己之謂信，充實之謂美」這段話為中心，於孟子性善論的思考脈絡之下，疏通其中意蘊，以求能一探孟子美善合一思想之勝義。

A special characteristic of Mencius' aesthetic theory is that he carried on the Confucian tradition of “the union of the beautiful and good”. （美善合一）He also made this theory the embodiment of. his most basic notion that “human nature is essentially good.”（本性善） This article would like to lay as a basis three aspects of moral emotion, moral reasoning and moral will, in looking at Mencius' theory of the goodness of human nature. These findings culminate in “the good” and “the beautiful” in a person. I would also like to examine Mencius' “A man who commands our liking is called a good man, he whose goodness is part of himself is what is called a real man, and he whose goodness brims over is called a beautiful man”, as the crux of this article. From his consideration of man's essence as good, we can bring light to the profundity of his meditations on the synthesis of the beautiful and good.