Selenium is a metalloid that it is antioxidant characteristics is proved for humans, animals and plants. However, some plants are known as hyper accumulators for selenium and sometimes seems to be useful for growth of some plants. In this paper, we have studied the effect of different selenium concentrations on growth and morpho-physiological characteristics of spinach. Seeds of spinach were germinated in germinator and seedlings were transferred to hydroponic cultures. The seedlings were grown in Hogland´s solution with different selenium concentrations (in form of sodium selenite) of 0,1,2,4,6, and 10 mgL-1 SeO3-2. The experiment was conducted based on a completely randomized design with four replications. Four weeks after treatments, morphophysiological characteristics including plant biomass, length of shoot and root, number of leaves, amount of chlorophyll a and b were measured. The results showed that application of different selenium concentrations had significant effect on morphological and physiological characteristics of root and shoot consisting wet and dry weight, root and shoot length and amount of chlorophyll. In this experiment, increasing selenium concentrations (except in 1 mgL-1 SeO3-2 concentration) decreased amounts of all mentioned characters in comparison with control. Morphological symptoms of selenium toxicity on spinach was chlorosis on young leaves and significant reduction in root and shoot growth.