Abstract: In this paper, crop water-production functions, namely crop water-yield models, of wheat, maize and cotton were analyzed and intrinsic relations among the different models advanced. Models of water-production function of different crops were fitted based on least-square theory using field experimental data from various irrigation regions, with quadratic model used for the whole growth period and Jensen model for growth stages. Water sensitivity index resulting from the fitting shows a low-high-low trend during the growth period. The results could provide agricultural irrigation practice with vital reliable academic hits to optimize irrigation systems in water deficient regions.