Traceability has become an effective method of ensuring food safety and connecting stakeholders in the food chain. There is an increasing growth trend in developing IT-based traceability system in recent years. But implementing hastily traceability system is likely to fail to achieve its goal if the system requirement has not been well-defined according to the changing business environment. This paper adopted an evolutionary prototyping model and used longitudinal case study to elicit the traceability system requirement at the level of agribusiness. The results show that a traceability system can support not only information tracking at operational level, but also diagnostic analysis and strategic decision making at managerial level, Hence, system requirements can be categorized as fundamental, decisive and strategic levels. The evolutionary prototyping model can improve the effectiveness of requirement elicitation.