In order to investigate the relationship between microstructures of inorganic electrolyte aqueous solutions and crystals formed from them, the high concentration sodium chloride aqueous solutions were researched by molecular dynamics simulation based on Lammps software and the results are discussed in combination with those of low concentration sodium chloride aqueous solutions and potassium chloride aqueous solutions. The water molecules are modelled by the SPC/E model and the interactions between particles is described by Coulomb interactions and Lennard Jones potentials. The mass fraction of sodium chloride is 28.21% in the solution, pressure and temperature are 1 atm (1 atm=101.325 kPa) and 380 K, respectively. The analysis results of ion clusters show that the composition and the geometric relationship of the crystals formed from the electrolyte aqueous solution correspond to those of the ion clusters in the solution, indicating that the composition and the geometric structure of the crystals formed from the solution already exist in the parent phase solution and that the crystals have a corresponding relationship with the microstructure of the solution. The results of the radial distribution functions, distances between ions and snapshots show that only directly-contacting ion-pairs and partially-spaced ion-pairs exist in the high-concentration sodium chloride aqueous solution, corresponding to the first and second peaks of Na⁺-Cl^- radial distribution functions in turn. Compared with the results of the low-concentration sodium chloride aqueous solution, the proportion of directly-contacting ion-pairs and that of partially-spaced ion-pairs respectively increases and decreases significantly while completely-spaced ion-pairs disappear, indicating that the pairing mode of ions would change with solution concentration; the transformation of the pairing mode of ions is the reason for the variation of the microstructure of solutions and for that of the structure of the crystals formed from solutions. The existence of pure water clusters composed of water molecules and ion clusters composed of Na⁺ and Cl^- in the solution states that the self-concentration effect is presented in the high-concentration sodium chloride aqueous solution. The results in this paper could provide an insight into the understanding crystallization and microscopic structure of solutions.