In this study, 55-year observing meteorological data were collected and used to calculate the water requirement of reference crop by applying Penman-Monteith formula. Crop coefficient of rice was determined by combining measured data for years with the single time average method. Single crop coefficient approach was used to calculate water requirement of rice. And the water consumption of rice and the irrigation quota were calculated in various partitions and irrigation types of Nanjing in different hydrological years, according to water balance principle combined with shallow-wet irrigation system. Based on the fact that the probability of future rainstorm during rice growth period is increasing, we present a rain water storage and controllable irrigation mode suitable for the generalization in Nanjing, to reduce loss of water and increase rainfall utilization rate. The results indicate that the effective utilization rates of rainfall in common drought years are between 70%~85%, and can reach nearly 100% in extreme drought years.