Abstract: The present work focuses on the microscopic elastoplasticity deformation and overall elastoplastic behaviour of metal matrix composites reinforced by short fibers.It is assumed that the fiber is elastic and the matrix elastic-viscoplastic.The nonliner finite element method is applied to investigate the elastoplastic stress fields of a unit cell,and the homogeneity method based on the volume average conception is used to find the overall stress-strain relations of composites.The interaction mechanism of fiber-fiber and fibermatrix is emphasized in this paper.