Disclosed is a method for leaching beryllium from low-grade bertrandite through microwave pretreatment. The content of beo in the low-grade bertrandite is 0.2-1.0%. The method comprises the following operating steps that A, crushing and ball milling are conducted, specifically, after crushed, the low-grade bertrandite is ball-milled, and the granularity of the ball-milled bertrandite is smaller than 200 meshes; B, microwave pretreatment is conducted, specifically, concentrated sulfuric acid and the ball-milled bertrandite are put into a stirring tank to be mixed evenly, the mass ratio of the concentrated sulfuric acid to the ball-milled bertrandite is 1.4-2:1, then the evenly stirred and mixed bertrandite is put into a microwave oven to be heated by microwave, and then heat preservation is conducted; C, leaching is conducted, specifically, the pretreated bertrandite is taken out from the microwave oven and put into a leaching tank to be cooled at the normal temperature, when the temperature of the bertrandite is lowered to 80 DEG C-100 DEG C, tap water is added for stirring and leaching, and the mass ratio of the tap water to the bertrandite is 2-5:1; and D, solid-liquid separation is conducted, specifically, after leaching, solid-liquid separation is conducted, a beryllium leachate is obtained, then beryllium slag is washed with tap water, the mass ratio of the tap water to the beryllium slag is 1-2:1, and washing liquid returns to the leaching tank.