Abstract: This paper discusses the sensitivity of fault in fault diagnosis when structural elimination method is applied.Fault diagnosis in the structural elimination is based on mathematical model and measured parameters.Because the measured parameters vary with the different faults,it is necessary to make deeper analysis when employing (0,1) fault matrix to reduce the possibility of making wrong diagnosis.The analytical method mentioned above which uses the sensitivity matrix is proposed in this paper.The method of calculating sensitivity matrix and an example that uses the matrix are also presented.The sensitivity matrix as well as the sensitivity degree of parameters for fault is compared with (0,1) fault matrix.The best test parameters can be chosen and the parameter’s combination can be eliminated according to different relationships of fault when the fault diagnosis system is designed by using the sensitivity matrix.Therefore,the reliability of the result of fault diagnosis will be improved.