As the basic unit at sub‐microscale, mineralized collagen fibrils are closely related to the extraordinary mechanical properties of bone, which has inspired the design of biomimetic materials. The original staggered structure model has not taken the porosity of lamellae and its influence on the distribution of fibrils into account, which result in the inhomogeneous stress in the hard phase. According to the image from the authors’ experiment, a structure model of biomimetic composites with porosity is proposed. The constitutive relations of the original model and the new model are established, respectively. On this basis, mechanical properties with respect to the aspect ratio of the hard platelets are studied. Finally, the two structure models are simulated by the finite element method. The results reveal that the new structure has a more uniform stress distribution under external force. So it has higher stiffness and strength mass ratio, stronger toughness, and maintains a relatively high‐damping coefficient. It is illustrated that the new structure model can give full play to the mechanical potential of each phase in the composite. The findings are of great significance to design biomimetic materials with superior mechanical properties.