Customer participation is considered as critical characteristic to differentiate service production and delivery from common goods production. Customer participation can be seen everywhere. Why does a customer participate in the process of Co-creation? The previous literatures were unable to agree or decide which had been right. After reviewing literatures and indepth interviews, we draw out eight main factors as a set of indexes system to explain the motivation of consumer participation, and establish an analytical framework of three dimensions. Based on Grey Relational Analysis (GRA) methods to analysis the uppermost factor, we conclude that “personal interaction” and “information exchanging” take more effect on customer participation.