Abstract: Taking wheat cultivar Bainong AK58 as test material, a field experiment was conducted to study the grain- filling processes in winter wheat under sprinkler and surface irrigation conditions in order to investigate the differences among grain-filling characteristics of different irrigation methods. The results showed that the data of grain weights were fitted to the nonlinear cumulative Richards growth model as a function of days after anthesis. Grain growth analysis based on Richards equation indicated that compared with that under surface irrigation condition, the final grain weights of the superior and inferior grains on sprinkler irrigation condition was markedly higher. Sprinkler irrigation increased the initial grain growth potentiality, shortened the time reaching the maximum grain filling rates, and enhanced the average and maximum grain filling rates in both superior and inferior grains. The grain filling rates in the superior and inferior grains were increased while durations were shortened on sprinkler irrigation conditions during the early grain filling phase. During the middle and later phases, both the rates and durations of grain filling were increased in the inferior grains under sprinkler irrigation conditions, while the grain filling rates were increased and the grain filling durations were not changed significantly in the superior grains. In conclusion, the magnitude of the effects of sprinkler irrigation on grain filling was quite greater for inferior grains than that for superior grains. The increment of grain weight of winter wheat treated with sprinkler irrigation was mainly realized through increasing grain weight of inferior grains.