Abstract: The present experiment was carried out to investigate the relationship between the crop water stress index(CWSI) and soil moisture content for irrigated spring wheat at Xiao Ba Kou irrigation station of Gansu province during 2001 March to July. The soil moisture estimation formula based on CWSI and soil water adjust coefficient which adopt power function model was gained according to crop ET_a under water dificit condition and CWSI definition. The experiment results show that the model is liable to overestimate soil moisture during whole growth stage, and the estimating value is approach to real soil moisture and the error ratio is less than 18%.