Recently, many companies want to accept and operate ERP (Enterprise Resource Planning) system in their fields ERP does not only include business, but also include finance, account, trade, personnel and BPR(Business Process Reengineering). Especially, it is necessary to have ERP system for companies which have lots of external business such as trade and communication sector. And then, in this paper, I will think about OLTP (On-Line Transaction Processing) system for operating ERP system and improve its defects that can operate more effective sales, circulation, demand plan. But it is regrettable that I can not make a comparative analysis with other systems because the ERP system is still on the introductory stage for the company studies and the benefits have not been realized yet. Another limitation of this research is its narrow scope of study in which only the raw material inventory system for a single company is covered. In the future, however, ERP system would be adopted by many corporations, which would help us to launch a comparative study on the results of ERP system implementation as a future direction of research.