Abstract: A new method to measure the diffusion coefficient of ion diffusing through the nanochannel is proposed.In this method,the variation of the solution resistance between the two ends of the nanochannel is measured,with which the variation of concentration is also obtained.Then limited diffusion theory is used to calculate the liquid diffusion coefficient（LDC） through nanochannel.With the system proposed,the diffusion coefficient of KCl solution through nanochannel is measured successfully.The results show that the LDC through nanochannel is much less than that through macrochannel.And the effect of electric double layer and size effect for iron diffusion through nanochannel are also analyzed.