Traditional test methods of embedded system software impose on the object system and the result of the test are not accurate enough as expected. Non-interference test (NIT) method can solve the problem. Not same with the traditional test methods, NIT is completely non-interference to the object software. By analyzing the basic characteristics of NIT, an application model of NIT was set up. There must be three modules in this model, include static analyse module, dynamic analyse module and data gathering subsystem which tracks the object system by hardware. Static analyse module figures out the static characteristics of the object software and tells the other two modulus how to gather the state data of the object system and how to understand the data. In all steps of the test cycle, NIT does not add any instructions executed only within the test round into the object program.