Selenium (Se) is an essential element for human and livestock health with antioxidant and anticancer effect. Although Se is not an essential element for plant growth,but improve the plant growth. A hydroponic experiment was conducted in the greenhouse of Isfahan University of Technology in winter of 1391. The completely randomized design was arranged. Se in four concentration 0, 2.5, 5 and 10 µM and Nano-Se in0,1, 4, 8 and 12 mM was added to nutrient solution. The results showed that Se improved stem diameter, fresh weight of shoot, chlorophyll content and phenol. Nano-Se improved root volume, fresh weight of root, relative water content of shoot, internal stomata CO2, and leaf temperature and mesophyll conductance. Se and Nano-Se were effective in 10 and 4 µM, respectively.Root volume increased in 8 µM Nano-Se by 72.4%. Chlorophyll content increasd by 73% in 10 µM Se. N-Se was more effective than Se on mesophyll conductance and increased in 4 µM Nano-Se by 9.9%. Conclusively, Nano-Se and Se in 10 and 4 µM was more effective respectively on most vegetative,antioxidant and photosynthetic activity of tomato.