Abstract: It is an acknowledged and effective method to test real-time embedded software with ESSTE(embedded software simulation testing environment). The software architecture of ESSTE is described systematically based on UML and "4+1" views model. The contents in different views can coordinate with each other and particularly the software of ESSTE is divided into two system-level components in design view: real-time component and non-real-time component,which are organized by the pipe-filter architectural pattern. Configuration tool class is the key class for non-real-time component and model class, real-time variables class, scheduler class for the real-time component. Designed and implemented hereby, ESSTE-Basic reflects excellent quality characteristics, such as changeability, portability and so on. It has successfully been used for system-testing of several softwares, finding out a great of software faults effectively, through which both the correctness and the effectiveness of the software architecture of ESSTE are validated.