The invention belongs to the technical field of electret materials, and specifically relates to an inorganic microcrystalline electret material and a preparation method therefor. The inorganic microcrystalline electret material is prepared from the following raw materials in percentages by weight: 35-45% of silicon dioxide, 15-25% of zinc oxide, 15-25% of diboron trioxide, and 10-15% of magnesium oxide, with the balance being a performance modifier. The preparation method comprises: selecting and mixing silicon dioxide, zinc oxide, diboron trioxide and magnesium oxide, and melting same at a high temperature to prepare a composite powder material, which realizes multi-component compounding, and has a microcrystalline structure, a single and stable energy trap mechanism, and a symmetrical positive and negative charge retaining property; and preparing the composite powder material and natural wax or rosin in a molten state into a sol body, which is more convenient for coating a polished surface of monocrystalline silicon, and then selecting a specific heating rate and a heating stage value to enable the inorganic microcrystalline electret material to have a relatively high dielectric constant.