The global business is facing the intensive competitive environment. To overcome the competition, most enterprises contentiously try different information systems to strengthen their competition and to extent their businesses. In order to execute the enterprises marketing strategies effectively, business organization applies various software from in-house development to standard package software either made in Taiwan or made in nations. However, while implementing the information system into specific project, this software caused many obstructions in both project time framing design and project cost control. To exam this problem, we found there is no appropriate requirement and package software or tool to manage the system gaps analysis. The main purpose of this thesis is to solve the present package software problem and develop a method to meet the enterprise needs in system difference analysis. We use the Unified Module Language (UML), use case diagram, drawing , activity diagram, use case description and decision table to complete the difference analysis between package software and specific project. Applying this method, the user not only can control the difference between the requirement system and object system precisely, but also build a communication channel among the users, system analysis, and programmers. In addition, the method provides a trend of customized system to succeed the project on line