Negative Poisson’s ratio structures have attracted great interest due to its many excellent mechanical properties. In recent years, to improve the specific stiffness of the structure, the negative Poisson’s ratio structure is combined with composite materials. In view of the phenomenon that the composite auxetic double-arrow corrugated sandwich panels (DACSPs) are prone to defects in the complex preparation, transportation and assembly processes that would seriously affect the mechanical properties of the structure, the mechanical properties of carbon fiber-reinforced composite auxetic DACSPs with and without defects were studied through theoretical analysis and finite element analysis (FEA) in this article. Based on the classical laminated plate theory and Mohr’s theorem, the stiffness and Poisson’s ratio of the structure are first obtained theoretically, which is verified by comparing with the numerical results. Then the defect coefficient is introduced and the effects of different coefficients on the mechanical properties of the composite auxetic DACSPs are systematically studied. Finally, under the premise of the same defect coefficient, the influence of different defect positions on the structural mechanical properties is also discussed. The results show that the stiffness of the structure mainly depends on the defect coefficient of the structure, and not sensitive for the relative position of the defect. However, the Poisson’s ratio of the structure is mainly related to the defect coefficient and the relative position of the defect.