Abstract: In Nicomachean Ethics, Aristotle views equality as the essence of friendship.The equality in friendship not only means that the statuses of both are reciprocal, but also that their intercourse is fair.Meanwhile, it requires both not only mutual love and care, but also identically paying out and benefiting.In terms of the background, the equality in Aristotle's friendship can be seen as a reflection of the democracy of Grecian polis and the principle of equality in commercial trade in human communication;in terms of historical influence, it is the junction of the Grecian friendship and the Christian fraternity, the source and origin of the Pan-kinshipization in the social culture of modern west, and the moral base of people's equally communication in modern society.