To compare the properties of the hexanitrohexaazaisowurtzitane (CL-20)/ cyclotetramethylenete-tranitramine (HMX) cocrystal and CL-20/HMX blends, the cocrystal structure and blending structure with the molar ratio of CL-20 and HMX as 2：1 were constructed respactively. The mechanical properties,structure stability and radial distribution function of the cocrystal system and blending system were simulated by molecular dynamics (MD) method. Simulation and calculation results show that the cocrystal process of CL-20/HMX can significantly improve the antideformation ability and ductility of the system. The tensile modulus of the cocrystal structure is greater than that of blending structure. The maximum bond length(L_max)decreases in the order CL-20/HMX blends＞ε-CL-20＞β-HMX＞CL-20/HMX cocrystal. The structure of CL-20/HMX blends is sensitized by the interaction in which Van der Waals force predominate. The cohesive energy density (CED) value of CL-20/HMX cocrystal structure is far greater than that of CL-20/HMX blends structure. The low sensitivity of CL-20/HMX cocrystal system is caused by the existence of hydrogen bond CH…O with relatively short length.