Irrigation is required in the north of Hubei Province as scarce water resource and limited precipitation could not meet the water demand of rice growth. In view of this, we built a paddy rice growth model for northern Hubei Province based on ORYZA 2000 model according to the results of irrigation test at Changqu irrigation station. By using the proposed model, we simulated the variation rules of water demand and yield of paddy rice in different drought conditions (different growth periods and drought levels). Results revealed that the water demand and yield of paddy rice decreased with the aggravation of drought. On this basis, we obtained the sensitivity coefficients at different stages, and established the water production function of paddy rice in association with the Jensen model and the least squares theory. The results could guide the irrigation of paddy rice in northern Hubei Province.