The sodium bicarbonate saline soils contain plenty of clay minerals such as montmorillonite, which absorb a lot of exchangeable sodium cation in their crystals. The clay particles with highly diffusion and very low hydraulic permeability become a main obstacle for soil improvement. According to "effect of added electrolyte" and chemical exchange theory, the techniques using gentle salty water leaching for sodium bicarbonate saline soil improvement is proposed. Selection of water quality or mineralization for leaching depends on the concentration, SAR of the saturated extract solution of the soil needed to be reclaimed; the crop's salt tolerance; the relationship among EC, SAR and infiltration. The water quality for leaching is generally 1-3g/L. But as long as its EC is smaller than that of soil saturated extract solution, the saline soil would be improved by leaching. Determination of the crop water requirement is the key problem for leaching fraction design. The Hargreaves method which is relatively simple and accurate was used for crop water requirement determination in experiment area. Perennially, the water requirement of wheat-Chinese cabbage, corn and soybean is 528.5mm, 525.4mm and 479.4mm respectively; the water deficit is 127mm, 139.1mm and 104.5mm respectively; the minimum leaching amount is 31.8mm, 34.8mm and 26.1mm respectively. If increasing leaching fraction, the soil improvement will be more quickly. To calculate the crop water requirement and leaching amount for a specific year, the specific climate data such as temperature, precipitation are needed. The field experiment shows that the salt content, ESP of arable soil layer decreased 28%-50% and 80% respectively two years later by 250mm leaching fraction. The possible planting crop was only sunflower, but now can be soybean and corn. The land economic benefit is doubled.