The invention discloses a three-dimensional metamaterial which is provided with a plurality of periodically-distributed U-shaped structures. Each U-shaped structure corresponds to one pixel point in an image, and all the U-shaped structures jointly form the needed image; each U-shaped structure is composed of two arms and a bottom connected with the two arms, the two arms and the Z axis are in the same direction, the arms of the adjacent U-shaped structures are independent from each other and do not make contact with each other, and the included angle formed between the bottom and the X axis is theta, and theta is larger than or equal to 0 and smaller than or equal to 90 degrees. The invention further discloses a preparation method of the three-dimensional metamaterial, a gray level encoding and display method based on the three-dimensional metamaterial and a binary encoding and display method. By designing the specific metal structure unit, extra freedom degree electromagnetic wave regulation physical properties are introduced, the metamaterial can selectively absorb electromagnetic waves of different frequencies, electromagnetic waves of different polarization states can be absorbed completely or absorbed partially or totally reflected, and therefore the important role is achieved in encoding and imaging technologies.