Testing data generation system is an important guarantee for the realization of the maintainable, and effective automated testing of embedded software. In this paper, analysis of the characteristics of embedded software testing data is studied firstly. And then, the process of the embedded software testing data generation is put forward. Finally, the design and realization of the ESTDGS (embedded software testing data generation system) are described in detail. Using the layered architecture design, the user layer, function layer and data layer of ESTDGS are separated and the generated testing data is eventually stored using XML (Extensible Markup Language), which can improve the generalization, maintainability and expansibility of the system effectively.