Abstract: Based on the constitutive,(quivalence theory of the multiphase solids and the microscopic mod1 of interficial damage,an analysis for the plasticity of the particulate-composites is complcacd in this paper.With the combination of theoretical formulations and the numerical calculation the macroscopic initial yield function,including the effects of the physical propcrty of the constituents,the geometric conditions and the interficial.damages,is expressed.A comparison the test values shows the reliability between the numerical results and of the theoretical analysis.