Salinity is one of the major environmental stresses that can inhibit plant growth and development and cause physiological and metabolic changes. In this study, a pot experiment was performed involving two-year-old grape seedlings. Three different concentrations of NaCl solutions composed of tap water were used to irrigate the potted grapevine in the presence and absence of a magnetic device. The growth parameters and photosynthesis characteristics were analyzed during the stress treatments under field conditions. The results were as follows: Compared with those of the plants irrigated with non-magnetized saline water (NMSW), the growth of the aboveground parts (growth quantity, internode length, basal diameter, leaf area and leaf number) and the root growth (total root length, surface area, mean diameter, volume and root tip number) of plants irrigated with magnetized saline water (MSW) increased in response to the different treatment solutions, and the biomass of the leaves, stems and roots increased by 2.0 %∼45.0 %. The proportion of material allocated to the leaves and roots increased, and the root/crown ratio increased when exposed to 6.0 g·L−1 NaCl solutions. Compared with those in the plants irrigated with NMSW, the chlorophyll a, chlorophyll b and carotenoid contents in the plants irrigated with MSW increased by 3.0 %∼13.0 %. Moreover, compared with NMSW, MSW led to increases in the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), limiting value of stomata (Ls) and water-use efficiency (WUE), while the intercellular CO2 concentration (Ci) decreased. The ratio of specific activity parameters per unit area exhibited the largest increase (from 12.0 % to 26.0 %), and photosynthetic performance indexes increased by 18.0 %–56.0 %. Generally, the abovementioned results indicate alleviated inhibition of grape growth under irrigation with MSW. Moreover, treatment with MSW reduced the damage of saline water to the photosynthetic mechanism in grapevine, helped maintain the photosynthetic activity in the mesophyll cells, and promoted efficient electron transport between the photosystems, thus promoting the biomass production of the grapevine.