Abstract: The growth and development of Bt transgenic cottons and their parent cultivars in different levels of salinity were studied in sand-culture. Results show that with increase in salt stress, leaf water potential, chlorophyll content, plant height, and dry matter accumulation of both Bt transgenic cottons and their parent cultivars decrease. Photosynthesis initially increases, but then decreases with increase in salt stress. Under constant salinity stress Bt transgenic cotton, “Bt321” and “Guokang 1”，responds stronger to salt stress than their parent cultivars,“Shiyuan321” and “Simian3”，as evident in leaf water potential, chlorophyll content, plant height, dry matter accumulation, and the like. However, in comparison with “CCRI30” and “CCRI16”, Bt transgenic cotton shows low tolerance to salinity.