To explore and compare the stability and mechanical properties of hexaazaisowurtzitane/polyvinyl alcohol (ε-CL-20/PVA) and ε-CL-20/PEG (poly(ethylene glycol)) composites on (001), (110) and (020) crystalline surfaces, molecular dynamics (MD) simulation was conducted for the ε-CL-20/PVA and ε-CL-20/PEG composites by COMPASS force field at room temperature under atmospheric pressure. The cohesive energy densities (CED), the binding energies (E_bind) and mechanical properties (tensile modulus E, shear modulus G, bulk modulus K, Poisson ratio ν and Cauchy pressure C₁₂-C₄₄) were obtained. Results show that the cohesive energy densities of ε-CL-20/PEG composites are greater than those of ε-CL-20/PVA composites, indicating that the stability of the former is superior to that of the latter. For the same composite, the order of CED is (020)>(001)>(110). For the same crystalline surface, the binding energy with PEG is greater than that with PVA. The order of binding energy is (001)>(110)>(020). According to Poisson′s ratios and K/G values, the elasticity and ductility of ε-CL-20/PEG composites are all better than those of ε-CL-20/PVA composites.