Abstract: In order to reveal the effect laws of non-woven short fiber tissues on interlaminar fracture toughness of carbon fiber-reinforced polymer (CFRP) laminates, the mode I interlaminar fracture toughness of CFRP laminates toughened with non-woven carbon fiber tissues of different areal densities (1.95, 3.90, 7.80 and 15.60 mg/cm²) and different average lengths of fibers (0.8 mm and 4.3 mm) were investigated. The experimental results show that for the CFRP laminates toughened with different short fibers, the toughening performance of short fibers whose average length is 0.8 mm is better than that of short fibers whose average length is 4.3 mm, and the non-woven carbon fiber tissue with the areal density of 7.8 mg/cm², thickness about 150 μm and average length of 0.8 mm significantly enhances the interlaminar fracture toughness of CFRP laminates, the energy release rate is improved by 99% at best comparing with that of unmodified CFRP laminate. The optical microscopy observation results show that the short fibers whose length is 0.8 mm have 3D interleaved structure in epoxy matrix, the structure can prevent the cracks form propagation effectively. SEM observation results indicate that the debonding and pullout of short fibers from epoxy matrix and plastic deformation of epoxy matrix around short fibers are the main toughening mechanisms of CFRP laminates. The research conclusions lay down the foundation for application of short fibers toughening technique for laminates.