The invention discloses aerogel micro powder and a preparation method thereof. The method comprises the following steps: a hydrogel is provided, and fragmentation is carried out on the hydrogel and dispersing the hydrogel to obtain gel fluid or gel dispersion liquid; an atomizing device is employed for performing atomization on the gel fluid or the gel dispersion liquid, gel droplets are formed, the gel droplets are collected by a low-temperature container, and the gel freezing particles are obtained; the freeze drying is carried out, and the aerogel micro powder is obtained. The aerogel micropowder can realize integration of granulation and refrigeration, pre-refrigeration is not required, rapid and continuous production of the aerogel micro powder can be realized, organic solvent displacement is not required, the preparation method has the advantages of simple process, short production period, low cost, energy saving, and environmental protection, the preparation process can be amplified to industrial production, and the obtained aerogel micro powder has the excellent physical properties of controllable morphology, uniform particle size, large specific surface area, high porosity amount, and low thermal conductivity.