Abstract: This paper analyzed moisture change and cotton on the foundation of the big field observation on-the-spot, for underground drop give birth to stage each to rise, quantity is surveyed, at the same time, cotton root is observed, The result is: underground drop fill the soil moisture change depth of cotton field major in 20~60 cm; cotton is thoroughly spread in 10~80 cm scope, major concentration in 15~50 cm, and have two obvious root departments layer; the rich happy cotton of reclamation area day the seedling stage of water consumption is 1.4 mm/d, bud stage is 2.3 mm/d, blooming and fruiting stage is 3.8 mm/d, boll opening stage is 1.5 mm/d, fill water system by this established this region.