Abstract: Based on the net charge conservation theory， a new theoretical framework was proposed to describe the ion concentration distribution and the potential distribution accurately in thin nanochannels of overlapped Debye layers. To verify whether the double electrical layers were overlapped， the classical PoissonBoltzmann equation was firstly employed to calculate the effective Debye layers thickness according to its definition. The double layers were overlapped when the effective Debye thickness exceeds the half height of the channel. Taking channel height， PoissonBoltzmann equation and reservior ion concentration into account， the assumption of net charge conservation can then be used to deduce the potential distribution and corresponding ion concentration. The calculated results showed that the electric potential difference between the surface and midplane will decrease with the reducing height of channel， which agrees well with the experimental data.

Key words: overlapped, Debye layer, nanochannel, potential distribution, net charge conservation