Abstract:Fault diagnosis is an important function of Automatic Test System/Equipment(ATS/ATE), whether the fault can be isolated quickly and accurately is an important factor affecting the maintenance efficiency of equipment. Nowadays, advanced automatic test system adopts ATML series standard usually for information interchange, the description of information such as test system,unit under test,test process,test results and diagnostic results using XML with the syntax and data structure is the key of the standard. The standard defines the fault diagnosis models such as Bayesian network, D-matrix reasoning,diagnosis logic and fault tree. Among them,D-matrix reasoning model can be easily established, it is widely usedin engineering because it is easy to realize. This paper build the Dependency model using graphic modeling method,and describes the method of establishing, the process of establishing,reasoningrules and reasoning algorithm of D-matrix model,and takes a radio station as an example to introduce the related description method of XML language.Finally,this paper analyses the testability of the radio base on the D-matrix, perfects the matrix and algorithm on the basis of the testability analysis result,it improved the radio fault isolation rate,and reduced the ambiguity group.