Mg/Al layered double hydroxide with two-dimensional (2D) nanostructures was synthesized by a hydrothermal technique. The morphology and aspect ratio of Mg4Al2(OH)143H2O were controlled by the concentration and kinds of the hydrolysis agent, and temperature. The aspect ratio of Mg4Al2(OH)143H2O layered double hydroxides with the 2D hexagonal crystal structure was tailored from about 12.6 to about 45.7. The intercalated CO32- anions of the synthesized 2D Mg4Al2(OH)143H2O layered double hydroxides were exchanged to NO3- anions. The bulk 2D Mg4Al2(OH)143H2O layered double hydroxides with the increased space between two layers due to the anion exchange were exfoliated in a formamide solution. The aspect ratio of the exfoliated 2D Mg4Al2(OH)143H2O layered double hydroxides increased to 570.3.