The invention provides a metal material with both high strength and high plasticity and a preparation method thereof. The metal material is characterized in that the crystal grains of microscopic structures of the metal material are composed of crystal grains with two different grain size ranges, and that is, the coarse crystal grains and the fine crystal grains. The coarse crystal grains are distributed in the fine crystal grains in a strip-belt shape. The coarse crystal grains are common micro crystal grains, and the fine crystal grains are nano crystal grains. The grain size range of the nano crystal grains is 10-200 nanometers, and the grain size range of the micro crystal grains is 0.5-10 micrometers. The preparation method of the metal material comprises the steps of multi-layer material preparation, cold rolling and recrystallization.