The paper presents a new service application in education area, namely credit bank. Credit bank is a service provided by authorized education organizations so that customers can save, manage and exchange education credits. The paper focus on establishing a service oriented information system to support the idea of credit bank. After introducing its concept, the paper studies the requirement of credit bank from both business and technical point of view. Then it presents a practical step-by-step guideline to identify services in the system. The guideline is applied to design credit bank information system (CBIS) as a case study. The contributions of the paper are: (i) It gives a new idea about how service can be used to benefit education; (ii) It presents a useful method for service identification in system design with case study.