There are great demands of today financial industry to achieve flexibility and growth by integrating new, innovative solutions with existing IT landscapes. Due to the economic climate that has prevailed over the past 18 months, outsourcing, in its different shapes and forms, has once again been gaining strategic significance in the financial services industry. Through literature research, we have found it is important to understand how to leverage application development outsourcing well in order to successful deliver the expected benefits. In this research, we have proposed using interview, literature search, practical empirical working experience as a basis for the methodology. We have interviewed senior managers of three major banks in Taiwan, on their applications on mainframe, midsize systems, and process management experience, and based on Outsourcing value-added method of Wu, and ¡§Method for different outsourcing successful factors for the life cycle of several industries¡¨ of Chun & Wu, etc. to derive initial critical successful factors (CSFs). We then collect knowledge of 26 success and failure outsourcing business cases, perform analysis and knowledge extraction based on xxxx ¡§comparison method¡¨ to conclude the critical successful factors for this research. From this research, we have found that the support from upper management to application development outsourcing is the most important. Due to their attention, many banks do provide training and education to their employees of the importance of leveraging outsourcing resource and how to perform a project teaming and management based on resources from internal employees, outside vendors, and contract employees. The important factors for teaming effort including, people communication, commitment, responsibility and working attitude, financial legal regulation, knowledge management and sharing, project management capability, human factors and relationship. Another factor is on the attention to the details of the development life cycle management to ensure its feasibility for requirement, completeness for clearance, and professionalism for outsourcing project management and knowledge. At the initial stage for team formation, it is important to describe the details of work breakdown structures and working products with the responsible person assigned. During the process of RFI, RFP, open bid process, vendor selection, price and contract negotiation, contract responsibility details, both sides need to pay attention of clear specification of responsibility, mutual respects of professional judgment, potential changes and risk management, deliverables, and after services and support. At every stage of the project, periodical checking on progress, difficulties, changes, progress stages and tracking, and early warming system, etc. are important to the success for project management. Individual team member¡¦s professional capability, communication skills, and initiative and working attitude are also the important factors for the successful factors. The last payment term can be an important factor too. This can be the unique situation in Taiwan. Some vendors would rather forfeit the last payment, but not finish the last commitment of deliverables or future supports. So sometime, keep a larger portion of the last payment can be a good resort to ensure long-term supports from vendors. In conclusion, we have found that vendor¡¦s attitude on service ability and customer relationship management, application owner¡¦s commitment to collaborate and timing support, maturity of supporting open-system based banking application, infrastructure for knowledge sharing among the project team members are the most important successful factors for the software development outsourcing. We do strongly recommend the leverage of outsourcing as a mean for the speedy improvement of new banking business process and innovative product creations for financial industry.