Abstract: A micromechanical method is used to study the elastoplastic behavior of metal-matrix composite reinforced by unidirectional fibers.It is assumed shat the fiber is linear elastic,the matrix is isotropic elastoviscoplastic.The elastic moduli and initial yield stresses are predicted under longitucinal tension,transverse tension and longitudinal shear deformation conditions, respectively,The effects of strain rate on elastoplastic response are in vestigated.As an example,the numerical results of Boron/Aluminum composite areobtained.The present predictions agree well wish the experiment results.