The properties of fiber reinforced metal matrix composites (MMCs) are anisotropic. These properties can be more appropriately evaluated in polar coordinate. In this paper, the elastic-plastic mechanics model of MMCs is presented based on the combination of macroscopic and meso-scopic analysis in polar coordinate. The influence of micro-parameters such as matrix materials, the fibers and fiber volume fraction of Al/Mg metal matrix composites (MMCs) on the tensile properties of MMCs is also investigated numerically by the representative volume element (RVE) and the numerical results are compared with the experimental data. The results show that the model built in polar coordinate is suitable to the real constructs of MMCs; the fiber plays a major role of load supporting during MMCs stretched. And there is little distinction of the value of maximum stress of MMCs between tests and the numerical analysis.