A field experiment was conducted to study the soil water-salt distribution and cotton growth using magnetized water for mulched drip irrigation. Results showed that magnetized water used in the experiment could improve the soil water retention and holding capacity effectively, and promote the water absorption of cotton roots. The soil moisture content of 3 000 Gs magnetized water irrigation treatment was highest at the soil layer of 0-100 cm. The magnetized water irrigation could reduce the soil salt content effectively, due to the magnetized water treatment could facilitate the soil salt leaching from the main root area of cotton into the below. At the 0-100 cm soil layer, the salt contents under magnetized water irrigation treatments were 3 000 Gs(low) < 4 000 Gs < 1 000 Gs < 5 000 Gs < 0 Gs. The soil desalination rates under mulched drip irrigation with magnetized fresh water were 2.7%~28.2%, among which the 3000Gs treatment had the most significate impact on reducing soil salinity. The soil desalination rates for magnetized brackish water treatments were 21.7%~33.9%. The magnetized water irrigation could improve the cotton biomass and output. The yields of seed cotton of magnetized water were increased by 8.98%~31.40% compared with ordinary water. The 3 000 Gs treatment was the best magnetic treatment by taking into consideration of both cotton output and water use efficiency.