The garments industry faces the paradox situation: high inventory and meanwhile serious out of stock because of various consumption demands and low accuracy of forecast. As the source of the whole supply chain, the traditional model of impulsive decision making is responsible for the inaccuracy and is changed to a new model of closed-loop, bicirculating with hypothesis and verification. For the new merchandising method, GeneXus is used to build up the information support system fast and conveniently. It shows that after deployed in enterprises, the application of the system can remarkably improve the prediction accuracy, reduce the inventory level and promote the sales performance. The feasibility of the new method and system is verified.