Abstract: By this pot experiment,the Na was lower than 500 mg/kg,the cotton growth was promoted obviously.When Na level was 1000 mg/kg,the seeding rate of cotton was only 60%,the sickness seedling rate reaches above 80%.And the biomass remarkably reduced.That is the marginal value of employment Na in cotton seedling stage.Under the condition of the low water-soluble K strength in the test soil,when K level is 120 mg/kg,and the supply of Na level is 80(mg/kg,) and the ratio of K2O to Na is 1∶0.67,accumulation of single sapling dry matter for the period of cotton seedling,bud and fllower-boll were increased remarkably.And the absorption of Na and K are the same.The production increased 8.96% to 10.28%.And the unginned cotton reached the most production.