There exit similarities as well as a great difference between embedded software testing and common software testing. Embedded system testing has close relationship to system software & hardware platform, and also has special requirements on test environment and test methods. Test case design is the core of software testing, which determines the effect of software testing. Software testing environment can be more easily injected for test case and directly affects the efficiency of software testing. This paper discusses embedded software testing techniques，analyzes the method to generate test case by using UML, presents the principle about adopting VI technique to construct simulation test environment. A certain embedded software system has been tested by using the methods proposed in this paper.