Abstract: Particle-reinforced composites have been used in some important aeronautical components, and the accurate prediction of their elastoplastic behavior is essential for material and structural design. This remains a key scientific challenge in the field of composite mechanics. In this paper, a micromechanical constitutive model with a consistent elastoplastic formulation for particle-reinforced composites is established based on the stress concentration factor. First, using classical micromechanical methods, the bridging tensor that describes the interaction between the particle and matrix in the linear elastic stage is derived to predict the linear elastic response of the composite. On this basis, the bridging tensor is directly extended to the plastic deformation stage, establishing a homogenization method applicable to plastic behavior, thereby achieving a constitutive model for the plastic regime that maintains the same form as that for the elastic regime. An analytical expression for the stress concentration factor is subsequently derived, which corrects the effective initial yield behavior of the composite and enables theoretical prediction of the elastoplastic behavior of particle-reinforced composites. Since the proposed model is extended directly from a linear elastic micromechanics framework, it features a concise formulation with physically meaningful parameters, facilitating its application in aeronautical engineering practice. To validate the model, representative volume elements of the composite are constructed, and numerical simulations are performed. The results demonstrate that the proposed constitutive model achieves good predictive accuracy. Furthermore, comparisons with experimental data confirm that the model accurately captures the elastoplastic behavior of real composite materials.