Abstract: Nano-indentation experiments and numerical simulations using ABAQUS software are performed to investigate the mechanics responses of energetic crystals. Continuous stiffness method based nano-indentation tests was employed to obtain the elastic modulus and hardness of β-HMX crystal (010) face and α-RDX crystal (210) face. The modulus and hardness can be induced from the load-displacement curves. The hardness value of the energetic crystals shows size effect. Microstructure fracture behaviors were analyzed using atomic force microscope (AFM) observations. It has been found that cracks initiate and expand with the increase of load force. The direction of the crack is also the cleavage direction of the energetic crystal. The finite element code ABAQUS is applied to simulate the nano-indentation experiments. Some parameters measured by the experiment have been used in validating the damaged plasticity constitutive model parameters for finite element simulations. The consistency between the experimental and the numerical simulated results is strong evidence for verifying the damaged plasticity constitutive model. The results presented here may be crucial in predicting the ignition mechanism of energetic crystals.