Abstract: A factorial pot experiment was conducted based on randomized complete block design in green house condition to investigate the effect of salt stress on photosynthesis, leaf carbohydrate concentration and daytime leaf carbon budget of two sugar beet cultivars (Madison and 7233-P₂₉) over photoperiod. Plants were exposed to 0, 50, 150 and 250 mM salinity (NaCl and CaCl₂ in 5:1 molar ratio) for 60 days. Measurements were done on youngest fully expanded leaves. Salinity caused a significant reduction in leaf net photosynthesis consequently total carbon fixed in both cultivars. However, salt stress significantly increased soluble carbohydrate concentration in both cultivars. Starch concentration of leaves also increased with increasing salinity. As salinity had inverse effect on photosynthesis process, the total carbon fixed decreased with increasing salinity. Daytime amount of carbon translocated from leaf was reduced by salinity.