In order to elevate the efficiency of the warehousing activities, a business has to avoid the mistakes of its staffs. This always results in the increasing of unexpected costs. Therefore, applying the warehouse management system ( WMS hereafter ) to deal with the warehousing activities is necessary. This case study incorporates the advantages of structured processes of IDEF3 with IDEF0 to do the reengineering of the WMS of the case company so as to make the communication among all the company more effectively, and this makes the WMS more applicable to the firm. This study considered the factors of time and cost. It analyzed the activity time of warehouse check-in, warehouse check-out and delivery, and then evaluate the improvement and efficiency of the whole processes.