Objective To study the effects of collagen fiber bundle on mechanical properties of articular cartilage, so as to provide references for clinicians to guide the rehabilitation of patients with early cartilage injury. Methods The two-dimensional (2D) numerical model of fiber-reinforced porous viscoelasticity was established, with consideration of the relationship of fiber distribution, elastic modulus, porosity and permeability with cartilage depth. The influences from local fracture of the fiber bundle, the progressive fracture from the surface and the fiber bundle size on mechanical properties of the cartilage were studied, and the maximum principle strain of cartilage matrix was obtained. Results The maximum principal strain of the matrix occurred at a position in middle layer of the cartilage, about upper 1/3 of the cartilage, which was not affected by fiber breakage mode and fiber bundle size. The strain of the cartilage with thicker fiber bundles decreased. Conclusions The middle layer of the cartilage was prone to mechanical damage. The thicker fiber bundle could reduce the maximum principal strain of the matrix. Once the fiber bundle broke, the maximum principal strain of the cartilage matrix with thicker fiber bundle became larger, leading to an easier evolution of the cartilage damage.