Abstract: Salinity is a major yield-reducing factor in coastal and arid, irrigated rice production systems. Rice seedlings cv. Tarom Azmoon was exposed to 200 mM NaCl for 14 days. Plant growth, relative water content, pigment and sugars content, photosynthetic efficiency and enzyme activity of rice seedlings grown under salt stress were investigated Shoot length of treated seedlings decreased to about 71% compare to the control. Salinity stress caused an increase in root length of seedlings. Root length of treated seedlings was about 54% more than the control. Fresh weights and dry weights of treated seedlings reduced to 95 and 75%, respectively. Salinity stress caused reduction in leaf relative water contents from 87% in the control plants to 74% in the stressed plants. The reduction of chlorophyll a and b contents of leaves was detected after NaCl treatment in leaves. Under salt stress, reduction of the chlorophyll b content of leaves (41%) was more affected than the chlorophyll a content (33%). The maximum quantum yield of PSII (FV/FM), photon yield of PSII (φPSII), non-photochemical quenching (NPQ) and net photosynthetic rate (Pn) in the stressed seedlings were inhibited, leading to overall growth reduction. The positive correlations between chlorophyll a content and Fv/Fm, total chlorophyll content and φPSII, Pn as well as Pn and leaf area were found. Sugar content in shoots had a significant increase under salinity stress. The starch content of roots seedlings decreased NaCI stressed seedling. The contents of total, reducing and non reducing sugars increased in roots.