In this paper, we consider a system in which both redox species are dissolved species as a model case. The Nernst-Planck-Poisson (N-P-P) equation is used to describe the mass transport including migration, with reference to Compton group. To the best of our knowledge, there are no reports of the transient-CV calculations using the N-P-P equation under the condition of no supporting electrolyte, probably due in part to the use of conventional Newton-Raphson (N-R) method that has problems with convergence in numerical calculations. We have successfully calculated CVs of electrode reactions with no supporting electrolyte in which the product is zero-valence by using the dumping-N-R method. In addition, we have derived an approximate analytical equation to describe the linear response of CVs.