The difficulty of Software Performance is how to obtain the performance evaluation quickly and accurately, and make it throughout the entire software development cycle. On the basis of the study on iterative development, a software performance platform is built with the help of modeling tools named UML and CPN. Make full use of the performance information provided by the UML document and the hierarchy of the CPN model and system architecture provided by multi-figure combination, it is easy to avoid one-sidedness in caused by a single UML diagram describing the system. Message which can describe the sequence of business processes and their probability is the main line of our study. Developing the easy-to-automate UML / CPN transformation rules, the CPN model translated into in the end would be transparent between different levels and clear between each interface. The Required performance evaluation data will be obtained by the use of CPN model simulation. Automatic conversion tools that are used to achieve transforming from UML to CPN and examples verifying the feasibility of the platform are in the end of this article.