Three-dimensional display technology, which aims at presenting almost-realistic three-dimensional images to the observer without any auxiliary devices, has drawn great attention from both academia and industry in recent years. In this paper, we implement a flat three-dimensional display using multi-layer semitransparent thin film structure. Compared to traditional three-dimensional display technologies, the proposed display technology has higher resolution, higher contrast, and simpler structure, thus easier to fabricate. Based on our prototype of flat three-dimensional display with multi-layer, we further extend it to spatial three-dimensional display using the principle of specular reflection, which allows observers to see virtual three-dimensional objects from different directions in the air.