The aim of this research is to develop a decision support system for partspurchasing. The decision support system is developed with Microsoft Access 4.0 andVisual Basic 4.0 on a microcomputer. This decision support system, Del_Plan is builtby using the knowledge of Decision Support System, Management Information System,Database System and Materials Requirement Planning. Del_Plan used to calculatequantity of purchase parts, delivery date and evaluate maker's rating. The decisionsupport system provides a decision maker purchasing plan and suppliers evaluation byusing 4 criteria: 1) conditions of purchasing 2) assembly plan 3) stock and 4) actualdelivery. This program is tested with the historical data. The result shows that thedecision support system can quickly process and provide quantity of purchase partsclosed to the used parts. Hence this system can decrease inventory value.