In view of the shortage of water resources and the serious degradation and low quality of natural grassland in Hexi Corridor, the reasonable water regulation and planting patterns were explored to alleviate the contradiction between grass and livestock, improve the ecological environment and realize the sustainable development of regional grassland animal husbandry. The experiment was conducted in a 2-year field trial to study the effects of three planting patterns (O: Sainfoin (Onobrychis viciifolia) monoculture, A: Sainfoin and Bromus inermis mixture, B: Sainfoin, B. inermis and Elytrigia elongate mixture) and four types of water regulation (upper and lower limits of irrigation were based on the proportion of soil water content in field capacity (θ_FC), W0: adequate irrigation (75%~85% θ_FC), W1: slight water deficit (65%~75% θ_FC), W2: moderate water deficit (55%~65% θ_FC), W3: severe water deficit (45%~55% θ_FC)) on soil moisture characteristics, hay yield, quality and water use efficiency of artificial grass. The results showed that: (1) In the temporal dimension (from April to September), soil water content in 0—40 cm soil layer decreased firstly and then increased, and this trend of W2 and W3 was more obvious than that of W0 and W1, and more obvious for monoculture than mixed sowing. Soil water content in 40—100 cm soil layer decreased gradually. In the vertical spatial distribution, the soil water content of each treatment increased firstly and then decreased, and then tended to be stable. The soil water contents of the three planting patterns were moderate variation, and the variation coefficient of surface layer and 60—100 cm soil layer was large. (2) With the aggravation of water deficit, the herbage yield of monoculture and mixed sowing decreased gradually, and the WUE increased firstly and then decreased. There was no significant difference in forage yield between W1 and W0 (p＞0.05), and the WUE of W1 was the highest. Compared with O, the two-year average total herbage yield of A and B increased by 16.01% and 12.74%, respectively, and the two-year average WUE increased by 18.64% and 11.19%, respectively. (3) Suitable water deficit improved the herbage quality, and the herbage quality of mixed-sowing pattern was better than that of monoculture. Compared with O, the two-year average ADF, NDF and CP in planting patterns A and B decreased by 4.40% and 2.73%, 2.82% and 2.02%, and 3.53% and 7.24%, respectively. However, under W0 and W1 water treatment, there was no significant difference in CP between planting patterns O and A. Compared with O, the two-year average Ash of A and B increased by 18.50% and 16.58%, EE increased by 23.19% and 20.37%, and RFV increased by 4.87% and 3.20%, respectively. Through comprehensive evaluation of principal component analysis, it was concluded that the combination of slight water deficit and mixed sowing of Sainfoin and B. inermis was the suitable water regulation and planting pattern for artificial grassland with high yield, high quality and high efficiency in Hexi Corridor.