Polybenzoxazine (PBO) aerogels were prepared from 4,4 '-diamino-diphenylmethane (MDA) benzoxazine monomer by HCl-catalyzed ring-opening polymerization at room temperature after CO2 supercritical drying. This study systematically analyzes the microstructures, thermal insulation properties, compressive properties, and thermal stabilities of the PBO aerogels. The aerogel structure was a cross-linked three-dimensional network with a pore size of 10-140nm. The conductivity of the aerogels was 0.035-0.057W/mK under ambient conditions, reducing to 0.009W/mK at 3Pa. The compressive strength reached 14.42MPa under 10% strains, much greater than in SiO2 aerogels of similar density (0.40g/cm(3)) reinforced by high-silica glass fiber, which is only 1.30MPa. Hydrogen bonding interaction was found to be critical for constructing the three-dimensional network structure of the aerogels. This work provides a valuable reference for exploring new structures and expanding the thermal insulation applications of PBO aerogels.