<正> In this paper, a systematic approach is proposed to obtain the macro-scopic elastic-plastic constitutive relation of particle reinforced composites (PRC).The strain energy density of PRC is analyzed based on the cell model, and the ana-lytical formula for the macro-constitutive relation of PRC is obtained. The strengtheffects of volume fraction of the particle and the strain hardening exponent of ma-trix material on the macro-constitutive relation are investigated, the relation curve ofstrain versus stress of PRC is calculated in detail. The present results are consistentwith the results given in the existing references.