A new method for optimal analog test points selection based on inner-and inter-class sensitivity factor and fault isolation degree is proposed.The inner-and inter-class dispersion of sampling data is calculated to define the test points’sensitivity factor

The test points is reordered according to the value of the sensitivity factor

and fault isolation group and degree of the reordered test points is computed by KNN network.The optimal test points set can be selected by the guidance of the proposed algorithm.Experimental analysis proved that the optimal test points set derived by the method has less test points

compared with other reference

the proposed method can select test poins set with higher fault diagnostic rate.