An anaerobic digestion device based on self-sustained air flotation includes an anaerobic digestion tank unit, a self-sustained air flotation screening unit and a biogas measurement and collection unit. The self-sustained air flotation screening unit includes an air flotation screening part, a material sedimentation part, a reflux part and a three-phase separation part connected sequentially from bottom to top. A digested material in the anaerobic digestion tank unit is pumped into the air flotation screening part, overflows into the material sedimentation part, and then is raised to the reflux part. Gas passing through the three-phase separation part and gas produced in the anaerobic digestion tank unit enter the biogas measurement and collection unit to be measured and collected.