Abstract: Based on experimental data for 5 years, the parabolic relations between cotton yield and water consumption are analysed, and the optimal water consumption for cotton is determined. According to the variations of stoma resistance, transpiration of leaves, abcission of squares and bolls in different soil moistures, the suitable soil moisture and drought indices in different stages of cotton are decided. The stochastic control model of irrigation for cotton could be used to predict dynamically effective soil water content and actual evapotranspiration of cotton and make the decision aiming at obtaining maximum economic benefit and water utilization efficiency