Carbon-based aerogels (CAs) have the advantages of large specific surface area, high porosity, good chemical stability, and high conductivity, which are widely used in energy storage, adsorption, catalysis, electronic equipment, and other fields. However, due to the inherent brittleness and high thermal conductivity of carbon materials, the practical application in the field of high-temperature insulation is greatly limited. In this paper, based on electrospinning combined with the freeze-drying method, PAN-based carbon nanofiber aerogels (PAN-CNF As) materials with stable structure, high mechanical strength (7.24 kPa), and excellent thermal insulation performance (0.0228 W m−1 K−1) were prepared by designing the structure specificity between the bulk properties of nanofibers and the freezing temperature.