Experimental study was conducted in arid environment of Minqin desert oasis to evaluate the effect of drip irrigation under mulch on soil moisture and onion yield.There were three treatments of drip irrigation under mulch and a CK of small border irrigation with different irrigation quotas(T1:2 490 m3/hm2,T2:3 030 m3/hm2,T3:3 570 m3/hm2 and CK: 8 100 m3/hm2) in the whole growing season of onion;and each treatment distributed different irrigation water amount in various growing stages.The result indicated that the highest use of soil moisture was obtained in T2 with the relative lower growing season irrigation,and its soil moisture use in 0~60 cm soil layer was higher than T1,T3 and CK by 10.73%,9.85% and 9.92% respectively.The highest yield and the highest water use efficiency were obtained in T3.The lowest water use efficiency was obtained in CK,which was lower than in T1,T2 and T3 by 35.28%,55.21% and 58.79% respectively.So proper increase of irrigation amount on drip irrigation under mulch can improve yield and WUE in Minqin desert oasis.