This study focus on the card slave problem, using Professor J.W.Forrest ¡¥s System Dynamic model to simulate the relationship between Card Holder and Banks, hoping to find a solution to help the slave problem. This study has the following conclusions. 1. Most Card Slave are made of their own consumption behavior, but this is only half the reason whey they ended up in debts. During the Credit Card promotion war, banks failed their responsibility and provided these card holder enough limit and not enough credit checks, which is another half reason why the problem occurred. 2. In general, Bank wants to maximum their profit by leaving their customers to pay as much revolving interest , for as long as possible. However, they failed to realize that as the time and debt goes by, card holder starts to lose their repaying ability, and this seriously effects the banks revenues when one day they just cant afford to pay anymore, the repaying ability is never consider in the banks credit limit policy, but it is in fact the most significant fact of them all. 3. Therefore it is best for Bank to use System dynamic method to monitor the repaying ability and dynamically adjust the credit limit and other factors to control the customers¡¦ wiliness to use their card.