Until several years ago, organizations mainly focused on optimizing business processes within organizational boundary. Enterprise Resource Planning (ERP) software had been a hot issue for companies to improve their operations. Towards the end of last century however, organizations increasingly included supply chain management, customer relationship management, and supplier relationship management in their roadmap for implementing information technology. Business-to-business (B2B) transactions and collaboration between organizations have received increasing attention. E-Procurement is an important issue of B2B transaction and collaboration. Stiff competition, fast changing customer preferences, shortening product life cycle, and product variety proliferation have pushed modern manufacturing industries to be more flexible to cope with their environments. Along with dynamic capacity allocation, efficient material procurement forms a pillar to support flexible manufacturing. Therefore, the implementation of e-procurement system in enterprise is an inevitable trend. Then the next issue comes to what benefit occur from e-procurement system? Most past research have addressed the benefit issue based on the case study of single enterprise. Little investigation has conducted quantitative research to assess the performance with respect to supplier and buyer. How to estimate the impact on performance for both of buyer and supplier as a result of implementing e-procurement system is the research issue addressed in this project. Given the web-based e-procurement system as the enterprise procurement platform, this research attempts to address the direct impact on business processes for buyers and suppliers simultaneously, and subsequently to evaluate the impact on performance for them. In addition, this research also intends to investigate the impact on relationship between buyers and suppliers. In fact, the motivation of supplier in implementing e-procurement system might be different from that of buyer, leading to different results which might occur. The questionnaire survey conducted in this research can help to evaluate the performance for buyers and suppliers.