Irrigation, leaching and salt pressing are the main measures for the amelioration of saline and alkaline land, but these measures also cause the phenomenon of salt return in soil plough layer due to the rise of groundwater. With the combination of closed drainage pipes, the desalination effect can be improved. In order to study the effect of different irrigation amount on soil water, salt and soil acidity and alkalinity distribution in saline and alkaline soil (with 30 t/hm2 desulfurized gypsum and 85.05 m3/hm2 fine sand mixed into soil tillage layer), under the condition of closed pipe drainage, three treatments were designed, namely, closed drainage combined with traditional irrigation, closed drainage combined with water-saving irrigation, and closed drainage combined with non-irrigation control treatment. By monitoring soil EC, pH and water content, the temporal and spatial variation characteristics of soil moisture, salinity and degree of acid and alkali were analyzed by combining traditional irrigation and water-saving irrigation with closed drainage. The results showed that compared with the control treatment, the traditional border irrigation treatment reduced soil moisture content, and the desalination effect of 0-20 cm soil layer was obvious. On the basis of closed drainage, EC values of 0-60 cm in oil sunflower field were 3.49- 0.67 dS/cm, 0-60 cm were 1.71- 0.33 dS/cm for water-saving irrigation and 3.75- 0.27 dS/cm for traditional irrigation. Although the conventional irrigation decreased soil salt in 0-100 cm soil layer after 10 D and increased the water content, the soil water content of 0-40 cm was still lower than that of the control treatment. Desalination effect of 40-100 cm soil layer was 2-3 times higher than that of the water-saving irrigation. The pH of 0-60 cm soil in the control treatment was 7.54-8.65, and 7.51-8.89 in water-saving irrigation treatment, which was close to that in the control treatment at 40-100 cm (8.29). The traditional irrigation treatment was 8.1-10.85, and the soil layer of 0-100cm in the water-saving irrigation treatment was dealkalized. High irrigation amount made the soil alkalization possible, especially in the soil layer of 20-40 cm. Under the condition of closed drainage, water-saving irrigation in the jointing stage of oil sunflower is conducive to soil desalination and dealkalization.