The ion selectivity of nanochannel due to the wall surface charges is capable of inducing strong coupling between fluidic and ionic motion within the system, which has been overlooked in the study of nanofluidics. This interaction opens up the prospect of operating nanochannel as nanoscale devices for electrokinetic energy conversion. However, the very short channel lengths make the ionic movement and fluidics inside the channel to be substantially affected by the ion depletion/accumulation around the channel ends. Based on three-dimensional electrokinetic modeling and simulation, we present a theoretical study of nanochannel electrical resistance. Our results show that by utilizing the short channel effect nonlinear I–V characteristics under small salt concentrations was observed and an improved 1-D model captures the major physics.