Service-oriented computing (SOC) is thought to be an effective way to tackle complex web-based business collaborations between enterprises in e-business environment, but in practice it didn?t reach the expectation. Current researches mainly focus on technological aspects, such as service publication, discovery, binding, and composition, etc, while lack in effective ways to support service identification and design before they are to be published and discovered by other enterprises. This paper analyzes the relationships between business service and inter- /intra-enterprise business processes, discusses what kind of properties a "good" service should have, and accordingly presents a Service Normal Form (SNF) and the corresponding service normalization method. In this method, the way of how to identify normalized services from business process models, and how to create close mapping between services and legacy component-based information systems, are emphatically discussed. This method provides great significance to help enterprises identifying and designing valuable business services.