The present paper is concerned with the thermal insulation property and evaluation of ablative performance of phenolic resin based carbon foam,which is prepared from phenolic resin,cyclopentane,tween-80 and P-toluenesulfonic via processes of foaming, solidifying and carbonization.The thermal insulation properties of carbon foam are investigated at 25 ℃，200 ℃，400 ℃ and 600 ℃ by LFA457 laser flash apparatus , while ablation resistance behaviors of carbon foam are studied using a custom built oxyacetylene torch test facility and the results are compared with that of C/C composites. The results show that thermal conductivity of carbon foam whose density and compressive strength of carbon foam are 0.3 g/cm³ and 11.7 MPa,respectively is 0.141 W（/ m·K）and 0.344 W（/m·K） at 25 ℃ and 600 ℃.The liner ablation rate of carbon foam is 0.03 1mm/s, and the back-face peak temperature of carbon foam is about 150 ℃ lower than C/C composites.On the contrary,the front-face peak temperature of carbon foam is about 400 ℃ higher than C/C composites.The conclusion is drew that carbon foam with low density has excellent thermal insulation property and ablation resistance behavior.