Salinity in soil or water presents a stress condition for growth of crops that are of increasing importance in agriculture.Crops differ greatly in their ability to survive and yield satisfactorily when grown on saline soils.Information on the relative tolerance of crops to a saline soil environment is of practical importance in planning cropping schedules for optimum returns.The relative salt tolerance of crops in the earlier growth period was investigated via pot culture tests with salinized light loam soil and four crop species in order to understand differences in salt tolerance of wheat,soybean,cotton and corn and its physiological mechanisms.The results obtained showed that cotton was the most salt-tolerant crop species and soybean was the most salt-sensitive one among four the crop species tested.Plant element analysis indicated that sodium concentration and sodium accumulation in all organs of crop plants increased sharply with the increase of soil salinity level.After absorbed by roots of wheat,soybean and cotton,sodium was transported to the aerial parts to certain extent.After absorbed by roots of corn,sodium was mainly accumulated there.It was only potassium accumulation but not potassium concentration in all organs of crop plants that decreased remarkably with the increase of salinity level in the media.Calcium concentration and calcium accumulation in all organs of crop plants decreased to certain extent with the increase of salinity level.After absorbed by roots of crop plants,potassium and calcium were mainly transported to the aerial parts.So potassium accumulation and calcium accumulation in the above-ground organs were more than those in the roots.K⁺/Na⁺ ratios in crop plants decreased with the increase of soil salinity.The large variations in responses of different crop species to salinity existed owing to difference in plant physiology,i.e.,difference in the ability to carry out special adaptive mechanisms.The results showed that cotton could absorb and accumulate more sodium in its organs under alkalinity level.Sodium could remedy the states of nutrition and water of cotton plant.So cotton was the most salt-tolerant crop species.After absorbed by roots of corn,sodium was mainly accumulated in the roots.Sodium concentration in the above-ground organs of corn was too low to suppress growth of corn plant seriously.