Abstract: Under the conditions of mobile rain-proof shelter and winter wheat cultivated in plots, effect of regulated deficit irrigation (RDI) on grain filling characteristics of winter wheat was investigated. A two-factor (growing stages introducing RDI and degrees of water deficit) randomized block designed experiment was employed in pot culture. The results showed that the grain filling course of winter wheat under RDI accorded with “S” growth curve of “slow-fast-slow”, which could be simulated well by Richards equation. There were significant differences among some of filling characteristic parameters under different water deficit treatments such as maximum filling rate and its appearing time, average filling rate, filling duration, active growing duration, and filling duration time of each filling phase as well as 1000-grain weight (GW). Light water deficit in wintering period had the highest average filling rate (0.234 g/d per 100 grains), biggest filling rate (0.369 g/d per 100 grains), filling rate of the third phase (0.099 g/d per 100 grains) , and 1000-GW (58.46 g). Results from correlation and stepwise regression analysis methods indicated that there were significant or very significant correlations among most parameters, in which biggest filling rate, average filling rate, active growing duration and filling rate of the third phase were significantly correlated to GW.