An infrared absorber based on Au/VO2 structure is designed in this paper. This tunable meta-material absorber consists of three individual layers of resonating patch, sandwich dielectric layer, and metallic background. Using the temperature-controlled phase change characteristics of VO2, some of the Tian-shaped Au structure is replaced by VO2, and the absorption peak, position and bandwidth of the absorber can be controlled by changing the ambient temperature. Because of the thermo-control phase transformation property of the VO2, the absorber is characteristic of different absorption effects at different temperatures. When the temperature is higher than the phase transition temperature, the absorber can form an absorption peak of 99.68% in the far infrared atmospheric window; when the temperature is lower than the phase transition temperature, the absorber can form two absorption peaks with absorption rates of 89.29% and 99.83% respectively in the middle and far infrared atmospheric windows. This paper analyzes the absorption mechanism of the absorber based on the surface current distribution and the surface magnetic field. From the mentioned above the paper finds that the anti-parallel distribution of surface current excites a magnetic dipole, which generates a strong magnetic resonance, achieving the effect of absorption. In the end, this paper researches the effect of electromagnetic wave polarization mode, incident angle and media material properties on the absorption properties of the absorber. The results show that the absorption is insensitive to polarization mode and incident angle. What's more, The absorption peak shifts its way in long wavelength direction with the increase of the dielectric constant.