Abstract: Low density ablative material is developed to shield the spaceship from the high-enthalpy, low heating rate thermal environment during re-entry. As new vehicle projects develop, the low density ablative material is required to be able to work in the new medium thermal flux environment. In this paper, material test pieces are evaluated in the arc heated wind tunnel with high-enthalpy, medium thermal condition. In the experiment, high-performance insulation material is installed between the water-cooled frame and test pieces, which avoids lateral thermal leaking and improves the accuracy of the experiment. It shows the competence of the low density ablative material under the new thermal condition in experiments. At the same time, the calculation is carried out to evaluate the thermal protection performance of this material. The ablative mechanism of the low density ablative material is very complicated. In this paper, the computation method for carbonization ablation is improved by making use of different predication methods in different regions, based on the heat conduction-pyrogenation-carbonization mechanism of the low density ablative material. The theoretical prediction is compared with the data from wind tunnel experiments, showing that the prediction is consistent with the wind tunnel result.