Abstract: Domestic T1100-grade carbon fiber composites often suffer from a ‘high strength but low toughness’ bottleneck due to their surface chemical inertness and poor interfacial compatibility. To address this, prepregs and composites were fabricated using CCF1100G fibers and epoxy matrices with varying toughening component mass fractions (0, 15, 25, and 35wt%). The synergistic effects of toughening content on the resin micro-phase structure, fiber/resin interfacial bonding characteristics, and mechanical properties of the composites were systematically investigated. The results indicate that increasing the toughening content induces reaction-induced phase separation in the matrix, evolving from a ‘sea-island’ to a ‘phase inversion’ morphology, which significantly enhances the fracture toughness of the resin matrix. However, the introduction of toughening components weakened the interfacial bonding quality between the matrix and the fibers, leading to a monotonic decrease in the single-fiber micro-bead debonding interfacial shear strength. The composite with 25 wt% toughening content achieves an optimal balance between matrix toughness and interfacial strength. It exhibits excellent static mechanical properties: a 0° tensile strength of 3565 MPa, a modulus of 190 GPa, a 0° compressive strength of 2088 MPa, and a short-beam shear strength of 122 MPa. Moreover, it demonstrates superior damage tolerance, with a compression after impact (CAI) strength of 363 MPa. This study provides critical insights for developing domestic T1100-grade carbon fiber reinforced epoxy resin composites in aerospace applications.