Based on the internal database as big data of X-Bank, 3,527 active customers with an initial length of service of more than 12 months, the method of data mining is concerned with the mathematic methods of K-Means of the cluster, Tree Decision, and Association Analysis are applied in the study. The findings show that with eight main products, such as VG (Visa Gold), VC (Visa Classis), MG (Master Gold), MS (Master Standard), VP (Visa Platinum), VV (Viva Violet Card), VA (Visa Auto Card), and others, VG and VC are the two top cards, in that the high-income customers, e.g. directors are more interested in VG card, while staffs concern VC card. In addition, using two cards, called the main card and the extra card, is popular. This is a potential chance for the bank to develop cross-selling products, which the product bundle strategies are packed into groups,