Soil salinity has become an important issue in agriculture. One of the most urgent global problems is to provide enough water and land to meet the world's food needs. Sodium in soil adversely affects the growth and yield of most crop plants, as most crop species are highly sensitive to saline conditions. However, it is estimated that approximately 15% of undeveloped land in the world's coastal and inland salt deserts would be suitable for growing crops using saltwater for irrigation. The idea of using seawater for crop production along coastal deserts has been proposed over the past 30 years. These alternative sources of water and land could be used for cultivation of specialized, salt-tolerant crops. Salicornia bigelovii, a plant that can be used to treat a variety of diseases, is one the most promising halophytes for cultivation in such areas. S. bigelovii is a leafless, fast-growing, annual succulent. It is one of the most salt-tolerant plants, and is capable of growing under highly saline conditions on salt marshes. Consequently, it is considered to be a promising crop for cultivation in subtropical coastal deserts. Unfortunately, high salinity and water scarcity still adversely affect the physiological functions of this plant. We investigated the effects of different concentrations of NaCl (0, 10‰, 20‰, 30‰, 40‰, 50‰, and 60‰) on growth, photosynthesis, chlorophyll and carotenoids contents, the contents of K⁺ and Na⁺, and components of the antioxidant system of S. bigelovii during the flowering stage. The results showed that the values for plant height, shoot biomass, chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), intercellular CO₂ concentration (Ci), and activities of peroxidase and superoxide dismutase in the shoot were much greater in plants in the 10‰ NaCl treatment than in those treated with higher concentrations of NaCl. Plant height and biomass were both significantly decreased in the 40‰-60‰ NaCl treatments. High NaCl stress resulted in decreased contents of chlorophyll and carotenoids, lower Pn, Gs, Tr, and Ci, decreased activities of superoxide dismutase and peroxidase, and lower K⁺ content. High concentrations of NaCl increased the contents of malondialdehyde (a product of lipid peroxidation), Na⁺, and Cl^-, and also markedly increased the Na⁺/K⁺ ratio. Correlation analysis indicated that the biomass of S. bigelovii during the flowering stage was significantly positively related to the chlorophyll a/b ratio, and was highly significantly positively related to plant height, Pn, Gs, Ci, Tr, chlorophyll content, K⁺ content, and superoxide dismutase and peroxidase activities in the shoot. In contrast, biomass was highly significantly negatively related to Ls, the carotenoids/chlorophyll ratio, malondialdehyde content, Cl^- content, and the Na⁺/K⁺ ratio. In summary, S. bigelovii showed optimal growth in the 10‰ NaCl treatment. Stomatal inhibition was the main cause for the reduction in Pn of S. bigelovii in the no-salt and high-salt treatments, while both stomatal restriction and non-stomatal restriction occurred in the 60‰ NaCl treatment.