In order to investigate the mechanical properties of the three-dimensional （3D） random fibrous （RF） materials under the service condition and improve the safe service performance and structural life of the thermal protection system （TPS）， a 3D finite element model of 3D RF materials with morphology characteristics was developed based on the finite element modeling software. The macro-mechanical properties of 3D RF materials related with geometric parameters （fiber direction， fiber length and diameter） in the TTT （Through-the-thickness） and IP （in-plane） directions was studied and the evolution law of mechanical properties of 3D RF materials in both directions was uncovered. The results show that the higher rate of sloped fibers in the material is， the higher TTT strength is and the lower IP strength is. As the fiber length increased， the compressive strength of the material increases until the fiber length reaches 0.9 mm. When the fiber diameter decreases， the compressive strength decreases. These results can be applied as the theoretical basis for the material production of 3D RF materials.