To research the effect of crystal defect on the stability, sensitivity and detonation performance of hexanitrohexaazaisowurtzitane(CL-20) /nitroguanidine(NQ)cocrystal explosive, the"perfect"and defective(adulteration, vacancy and dislocation)CL-20/NQ cocrystal explosive models were established. Molecular dynamics method was applied to predict the properties of various models. The binding energy, trigger bond length distribution, bonding diatomic interaction energy, cohesive energy density and detonation parameters of different models were got and compared. The results show that compared with the"perfect"crystal, the decreasing ampliture of binding energy of defective crystal is 4.29%-24.33%, indicating that the intermolecular interaction energy is weakened and the stability is decreased. The increasing ampliture of trigger bond length of defective crystal is 0.78%-6.04%, while the decreasing ampliture of bonding diatomic interaction energy is 2.86%-20.03% and the decreasing ampliture of cohesive energy density is 2.46%-12.72%, indicating that the sensitivity of explosive is increased and safety is worsened. Owing to the influence of crystal defect, the decreasing ampliture of density, detonation velocity and detonation pressure of explosive is 0.58%-7.57%, 0.43%-5.99%, and 1.19%-15.31%, respectively, indicating that the energy density and power are decreased. Therefore, crystal defect has a negative effect on the stability, sensitivity and energetic characteristics of CL-20/NQ cocrystal explosive, among them, the effect of vacancy defect on the performance of explosive is more significant.