Abstract: Fiber-reinforced resin matrix composites are widely used in the aerospace field, but due to the complex physicochemical properties of component materials and molding processes during manufacturing, they are prone to generating manufacturing defects. Based on this, this paper systematically reviews the existing manufacturing defects of three-dimensional woven resin matrix composites and their non-destructive testing methods. First, the formation mechanisms of defects within the matrix, fiber reinforcement, and interfaces are elucidated, with a specific focus on residual stresses, void generation laws, and resin-rich zones arising during the matrix curing process. The study reveals the multi-scale distribution characteristics of voids resulting from uneven fiber tow impregnation in the Resin Transfer Molding (RTM) process, as well as the causes of defects such as fiber misalignment and breakage. Secondly, the significant impact of reinforcement defects—including fiber wrinkling, waviness, and missing yarns—on material performance is discussed, alongside the damage evolution mechanisms of interfacial defects like delamination and debonding. Finally, the application of non-contact non-destructive testing techniques in characterizing multi-scale defects is summarized, emphasizing the emerging trend of intelligent detection driven by machine learning. This review provides theoretical support for the optimization of manufacturing processes and the enhancement of reliability for 3D woven composites.