The simulation of controlled object and environment are usually required for embedded software system testing to achieve the purpose of Hardware-In-Loop (HIL) verification. It is necessary to connect both the real time simulation model of controlled object and software to be tested to perform HIL testing. Based on the analysis of latest needs of embedded testing,a system platform in accordance with test automation of embedded software based on Distributed Simulation Testing Environment is proposed in this paper. The testing system implanted with powerful test management function,composed with not only the real-time simulation device as its core but also the modular customization of device interface connected,which actualizes the system level HIL hardware and software simulation environment of dynamic testing of embedded software system and brings out a solution that perfectly handles the defects of embedded system such as deficiency of memory and tightly related with hardware and so on.