The invention discloses a bivalent nickel ion activated near-infrared long afterglow nano material which takes ZnGa2O4 as a base material and is doped with 0.1 mol%-5 mol% of Ni. The invention further discloses a preparation method of the near-infrared long afterglow nano material. The method comprises the steps that 1, zinc acetate, gallium nitrate and nickel nitrate serve as the raw materials, the raw materials are added into a mixed solution of water and ethyl alcohol and stirred at room temperature, acetylacetone is added, the mixture is stirred at room temperature, and a mixed solution is obtained; 2, the mixed solution is dried, and wet gel is obtained; 3, a mixed solution of n-butyl alcohol and ethyl alcohol is added into the wet gel, reacting and drying are conducted in sequence, and dried gel is obtained; 4, the dried gel is ground and then transferred into a crucible, burning is conducted in a smelting furnace at 900 DEG C to 1,200 DEG C for 2 h, and a power material is obtained. The afterglow bandwidth of the near-infrared long afterglow nano material ranges from 1,050 nanometers to 1,600 nanometers, the afterglow peak is located at 1,250 nanometers to 1,350 nanometers, and the bivalent nickel ion activated near-infrared long afterglow nano material can be well applied to the field of bioimaging.