The interdependence model of Levinger and Snoek divides the development of intimate relationship into four stages: the first one is zero contact stage, which is no contact between the two parties in the relationship; The second stage is awareness, which means people don't have any superficial or deep contact with each other, but just know each other; The third stage is surface contact, in which both parties know each other and have had superficial contact; The fourth stage of coexistence phase (mutuality), refers to the mutual dependence has greatly increased, there are also deep contact existing,