Abstract: Experimental studies and finite element simulations are conducted to investigate the buckling and post buckling behaviors of carbon fiber 3D integrated woven spacer composites under out-of-plane axial compression loads. Firstly, the buckling loads of the material and the buckling failure modes of the pile warp under compression loads are studied. Then, based on the experimental results of specimens with different heights of pile warp, the influences of height of pile warp on buckling loads and failure modes are studied. Finally, based on a user-defined subroutine, a finite element model employing the Hashin failure criterion and a stiffness degradation criterion is established to conduct nonlinear buckling analysis of the material. Compared with the experimental results, the error ranges of the buckling loads are within 0.0%-10.9%, and the failure modes are basically coincident, which indicates that the proposed method can predict the buckling behaviors of carbon fiber 3D integrated woven spacer composites.