1.14～2.05GPa。The mechanical properties of wheat stems in mature were tested, and the curves on stress-strain of wheat stems were measured by the electronic testing machine CMT2502. The microstructure of wheat stems was observed, and the SEM images of transverse and longitudinal section of wheat stem were got by scanning electron microscopy. The relation between mechanical properties and microstructure of wheat stems was analyzed, and mechanical model of wheat stem was established. The results show that wheat stem is a typical porous, no-continuous, no-homogeneous and anisotropic composite material. Wheat stems have enough strength and good flexibility, and its carrying capacity depends on the thickness of thickwalled cells and the numbers of vascular bundles, as well as the connection form and strength of cells in stems. The strength and Young's modulus of wheat stems are 30.36～52.65MPa and 1.14～2.05GPa respectively.