Abstract: A method for locating node-faults in.linear analog circuits is proposed on the basis of fault diagnosis equations written in terms of node-admittance matrix. It improves the reliability of diagnosis by avoiding matrix inversion and reducing algebraic computations. Using the concepts of two-graph and common tree, the method replaces some algebraic computations with topological computations. In order to locate the faults, it needs only to find out'whether the two graphs possess a common tree. Thus,the method also provides a new algorithm for finding common trees in two graphs. The algorithm was realized on IBM-PC using FORTRAN. The flow chart of the algorithm and some illustrative examples are also given in the paper.