On-line optimization is a very powerful tool that saves costs and improves the operational productivity of a chemical plant. However, the process of on-line optimization takes too much time and cost because it needs the significant contribution of process optimization specialists. To solve this problem, a web-based support system for online optimization is designed. The design specifications of the target product are identified using product design tools such as house of quality and roof correlation matrix. The design specifications are implemented into three product modules: communication module, project management module, and information interaction module. The final prototype system is evaluated based on a real application to the on-line optimization of a PTA process. The system shows both the time and the cost could be reduced by 43.5% and 43.3%.