Reduced graphene oxide/phenolic resin （RGO/PR） hybrid aerogel was prepared by physical blending and ambient drying method based on sol-gel technology. The changes in the microstructure， thermal stability and dielectric properties of RGO/PR hybrid aerogel were investigated with the RGO content， and the application performance of RGO/PR hybrid aerogel as a thermal insulation/microwave absorption composite matrix was explored. The results show that the RGO lamellar structure is uniformly dispersed in the phenolic aerogel skeleton， and the addition of RGO can effectively improve the thermal stability of the aerogel. When RGO with a mass fraction of 4% is added， the T_max of the hybrid aerogel is increased by 17.28℃. RGO has a significant effect on the dielectric properties of RGO/PR， and the real part of the 2 GHz dielectric constant increases from 2.6 to 4.7， which can realize flexible regulation of the electric properties of PR aerogel. When the aerogel thickness is 20 mm， the minimum reflection loss is less than -10 dB. After the quartz fiber reinforced RGO/PR hybrid aerogel is ablated for 500 s at a surface temperature of 1 200 ℃， the maximum back temperature is only 186.31 ℃， showing good thermal insulation performance.