The present paper addresses changes in uptake, transport and allocation of potassium and sodium, SOD (superoxide dismutases) activity and H₂O₂ content in leaves of Bt (Bacillus thuringiensis) transgenic cotton (Sukang 103) induced by different levels of salt stress as compared with those in its conventional parent (Sumian 12) at the early growth stage.The results showed that after receiving Bt gene the cotton increased its demand for potassium; more potassium was accumulated in shoot while the potassium content in roots was lowered as compared with the regular cotton.It seems to indicate that potassium transport ability is enhanced.On the other hands, when both regular and Bt cotton seedlings were exposed to salt stress, the ability of selecting potassium for transport from root to shoot was weakened in the Bt transgenic cotton, consequently more sodium was accumulated in the shoot and salt tolerance was lower than that in the control.Furthermore, SOD activity in leaves of the Bt cotton decreased significantly under salt stress, which might lead to reduced ability of eliminating superoxide radicals (O₂^-).Results of the research suggest that Bt cotton is more sensitive to salt stress than regular cotton and may not be suitable for cultivation in saline soils.