Abstract: Alternately stacking needling technology is a straight forward way to prepare three-dimensional (3D) fabrics, but randomly needling process will bring great challenges to the damage evolution, mechanical analysis and property prediction. In this paper, the damage evolution of nanoporous phenolic composites reinforced by alternately stacking fiber felt and woven fabric was revealed by in-situ X-ray Micro-CT device. And the angle deflections of fiber were described quantitatively under the loading of axial tensile by automatic tracing of microtubule centerlines. Finally, based on the 3D reconstructed structure, a high-precision finite element analysis model was established, and the axial tension mechanical behavior analysis was carried out. The results show that the damage in composite starts from the outmost layer where the microcracks in the fiber felt mainly originate from the resin-rich zone in the needling area, while the microcracks in the woven fabric are among filaments in fiber bundle. Besides, the woven fabric can improve the toughness of composite by preventing the microcrack expanding into the inner. The fibers in composite will consistently deflect to the outside, showing the property of negative Poisson's ratio, avoiding the "neck contraction" phenomenon at the fracture. The finite element analysis agrees with the results of experiments. The methods and results in this paper can provide a precious reference for microscopic fracture analysis, property prediction and structural optimization of complex 3D composite.