Irrigation scheduling is very important under water stress condition. To investigate the crop water stress phenomena, several indices have been presented, of which one is CWSI. In order to investigate the ability of this index in irrigation scheduling of Maize (SC704), a research in a randomized blokes design with four experimental treatments was conducted in Khoram Abad region in 2011. Experimental treatments including IR1: 100% water requirement, IR2: 80% water requirement (by Regulated deficit irrigation), IR3: 60% water requirement (by Regulated deficit irrigation) and IR4: 50% water requirement (by Partial root zone drying management). The results showed that the amount of CWSI was significantly affected by water stress. The CWSI index for IR1, IR2, IR3, and IR4 treatments were 0.17, 0.21, 0.39, 0.29 and the amount of yield were 21560, 19500, 12560 and 14860 Kg/ha, respectively. In this study, the best treatment was IR1 (with the minimum CWSI and the maximum Yield) and the worst treatment was IR3 (with the maximum CWSI and the Minimum Yield). Based on CWSI index, the value of water stress in IR4 treatment was less than the water stress value of IR3 treatment (The CWSI index dropped by 11.4 percent and the amount of yield increased by 18.3 percent). In this research, the relationship between the corn forage yield and CWSI index was obtained with high correlation. Regarding the variation of CWSI under different treatments, it can be stated that the CWSI index is able to evaluate the water stress and estimate the corn forage yield.