Abstract: The effects of no mulching (CK), plastic film mulching (PM) and straw mulching (SM) on grain filling characteristics, yield, water consumption and water use efficiency (WUE) of summer maize under 3 water treatments (75%, 65%, 55% field capacity) were studied in a 2-factor complete randomized experiment. Results show that grain weight increase in summer maize under different moisture conditions is in accordance with logistic curve. Grain filling rate, yield, and WUE in treatments PM and SM are greater than those in CK. The degree of increase in yield and WUE in PM and SM under the medium moisture condition (65% field capacity) is highest with increase rate of 21.99% and 35.86% for yield, and 16.41% and 16.79% for WUE respectively. The rate of yield and WUE increase in PM and SM under low (55% field capacity) and high (75% field capacity) moisture conditions ranks second and third respectively.