This paper presents the priority of Key Success Factors (KSFs) on Enterprise Resource Planning (ERP) system implementation life cycle. There are twenty KSFs considered in this study. They were chosen from literature review. The KSFs are classified into five stages of ERP implementation life cycle; namely: project preparation, technology selection, project formulation, implementation/development and deployment. To address the study objectives, a survey questionnaire was considered the most appropriate research method. It was sent to 74 companies that have been implementing ERP system for at least one year. The respondents are staff at management level, IT staff and users involved in the development and use of the ERP system.