In order to explore the suitable lower limit of irrigation and rational irrigation times for the potato in the arid regions of Ningxia，the number of different field water holding capacity is used as the lower limit of soil moisture control to control the number of irrigation，and the different plant height，leaf area index and the different treatments are analyzed． Dry matter yield at the site，as well as WUE has impact on yield and water use efficiency． The results show that the minimum irrigation limit of 75% of the field water holding capacity of the average growth indicators are also large． For example，the lower limit of the tuber growth period is 70%． The average is 41．4 and 39．5 cm，and other treatment． There is a significant difference between the two groups ( P＜0．01) ，and there is also a certain role in delaying senescence at the late growth stage． The lower limit of irrigation is 70%． The maximum yield of Tianchi is 39 894．2 kg /hm2 ，but the water use efficiency WUE is 55% in the lower limit of irrigation，the average is 13．04 kg /m3 ，and the irrigation lower limit is 75%． The WUE is the smallest，averaging only 8．84 kg /m3 ． Fitting the relationship between the evapotranspiration and yield of potato． It was found that the index model had good results，and the coefficient of determination Ｒ2 reached 0．989 3． The analysis showed that when the potato ETa was greater than 440 mm，the potato yield drastically decreased，which was not conducive to water saving and the improvement of irrigation efficiency． Therefore，it is recommended that irrigation with a minimum irrigation limit of 70% of Tianchi be used as a reference for potato production in the region．