One of the most important functions of manufacturers and producers related to supply chain management issues and decisions is supply chain order management. However, there are several problems in this regard like (a) selection of best order portfolio between the received orders, and (b) detailed and accurate calculation of order fulfilling costs. Accordingly, in order to increase model confidence in the research, we used both mathematical optimization and system dynamics to design the order management system of an Automakers Company supply chain orders. In phase 1, using the mathematical optimization approach, we determined optimum order portfolio of the received supply chain. In phase 2, using phase 1 output and system dynamics approach, we determined the costs of order fulfillment. Both traditional and activity-based costing techniques were used to calculate cost parameters and objects. Ultimately, in order to select better costing approach, we compared the  two approaches. According to the results, ABC is better costing approach than traditional.