Abstract: Crop water stress index(CWSI) is widely used in determinating irrigation time but seldom in determinating irrigation water amount. The objective of this paper is to investigate the relationship between the CWSI and the soil moisture and the possibility of using it to determinate the irrigation water amount. Analysis of the CWSI of the different irrigation treatment plots indicated that CWSI increased with the decrease of soil water content and showed variations caused by fluctuation of the weather factors. The correlation coefficient of CWSI to soil moisture content was only 0.54. This indicates that CWSI may not be used reliably for determinnating the irrigation amount.