The morphological and nutritional characteristics on two ecotypes of reeds，upright and creeping reeds，which growing in the same soil (saline-alkali soil) and climate environment，were studied by the techniques of light microscope，scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and the methods of ions analysis. The results showed that compared with the ecotype of upright reeds，creeping reeds have higher contents of sodium，silicon and calcium，but lower content of potassium，and hard thick leaves that curled less at noon. Among the mineral ions in the plant tissues of the two ecotypes of reeds，Si was the highest in content，and followed by Na，and Ca. The distribution of sodium in the plants showed a pattern of being lower in the shoots than in the roots，and in the leaves than in the stems，while the distribution of silicon being higher in the shoots than in the roots. Analysis of the anatomical structure of reed leaves and X-ray spectrum of silicon therein revealed abundant Si on surfaces of the leaves and groups of large vacuolated bulliform cells on upper epidermis of the leaves of both upright reeds and creeping reeds. However，stretch of vascular bundle sheath cells near the upper epidermis was observed greater in the creeping reeds than in the upright one. And in the stems of the two ecotypes of reeds，Si distributed more concentratively in the part above a knot than below the knot and very little in between the knots. Si distributed evenly in the stem above the ground of the upright reeds，but concentrated on the side of the stem near the earth of the creeping reeds. All the findings above demonstrate that the morphological variation between the two ecotypes of reeds are closely related to the ion distribution. Low Na concentration and high Si concentration in leaves of the reeds contributes significantly to mitigation of damage of salt to the photosynthetic organ，and regulation of water supply and growth of the plants in the arid and salt-affected habitat.