Objective To study N-methyl-D-aspartate activated single-channel kinetics behavior based on 3- and 4- state model. Methods The distribution of single-channel parameters were calculated in the different Mg ion concentration and holding potential based on 3- and 4-state model and compared it with data from experiment. Result The block rate depends linearly on Mg ion concentration when Mg ion concentration was greater than 20 μmol/L, however, when Mg ion concentration was less than 20 μmol/L, it is independent of Mg ion concentration. Conclusion There is a second blocking mechanism in addition to the Mg block at very low Mg ion concentrations. It may be because of the result of a voltage-dependent conformational change.