A topological method for obtaining the Jacobian and Hessian matrices of active networks is presented. It is based on the replacement of the investigated network by using a nullor equivalent circuit and on the representation of the circuit passive part by a Chan-Mai signal-flow graph (CMSFG). The Jacobian and the Hessian matrix elements of the nullor network can be obtained by means of the some dependent variables of two or four isomorphic CMSFGs, respectively. Two examples illustrate the proposed method.