With the help of Bishop Ambrose and the "Milanese Circle", Augustine acquired a new understanding of how men are made according to the Image and Similarity of God (ad imaginem et similitudinem nostram)(Gen.1:26), and this enlightenment had become a key to his conversion to Christianity. He eventually broke away from Manichaeism's view of the body and understood that men are not similar to God in body but are bestowed with the Image of God in soul and spirit. (Conf. V.10.19, VI.3.4) However, he did not report the exact teaching of Ambrose in his Confessions. How did Ambrose interpret this problem in his own writings? Did Augustine fully accept Ambrose's interpretation? In fact, we should also reconsider the possible influences of the theories of "Form" and "Participation" of Neo-Platonism. Plotinus used the terms εἴδωλον and ὅμοιος to explain how lower beings participate in higher beings and try to imitate them, and especially, how the transcendent hypostases bestow on men and other beings Existence, Unity, and Form. Likewise, Ambrose used "Similarity" to signify different ontological degrees of man and other things and held that only Christ is the perfect and equal Image of God and has no dissimilarity to God. Augustine believed men could also be called image of God, but it is only similar and never equal. He also emphasized that men are made in the Image of the whole Holy Trinity. This article will also try to show that Ambrose had played a vital role in this transmission.