In contrast to the nonionic micelles, a diffusivity of ionic micelles can be a non-monotonic function of the total surfactant concentration. The results on the diffusivity in micellar solutions are usually obtained by dynamic light scattering experiments. Interpretation of the experimental data is typically based on a bimodal approximation for the distribution of surfactant aggregates which presumes that there are only monomers and stable micelles of certain size. More reliable is picture of dispersed aggregates, and here the methods of molecular modeling allowing one to look at individual aggregates and analyze the distribution of their sizes can be very helpful. The diffusivity of ionic micelles in aqueous solution as a function of aggregation number is studied via molecular dynamics methods. A molecular dynamics of aqueous solution of sodium dodecyl sulphate (SDS) at normal conditions is carried out using MDynaMix package. An all-atom representation of SDS and solvent has been employed, CHARMM36 force fiel