The effects of water-nitrogen coupling on biomass yield，quality and water and fertilizer use efficiency of switchgrass are studied by randomized block experiment using ‘Cave-in-rock’ switchgrass in the saline-alkali area of Yinbei，Ningxia.The changes characteristics of biomass yield，quality and water and fertilizer use efficiency of switchgrass under different water and nitrogen treatments are studied by using the method of Fuzzy similar priority ratio.The results show that under the conditions of saline-alkali soil，adequate irrigation and appropriate nitrogen fertilizer input are the guarantee for high yield and efficient utilization of water and fertilizer for switchgrass.Under the same irrigation conditions，medium nitrogen treatment significantly increases the yield，cellulose，hemicellulose content，water use efficiency，nitrogen agronomic efficiency and nitrogen use efficiency of switchgrass.Under the same nitrogen application rate，with the increase of irrigation，the yield of switchgrass increases，and the contents of cellulose，hemicellulose and ash decreases first and then increases.Medium nitrogen treatment can maintain low ash under different water conditions，and can obtain the highest yield，nitrogen agronomic efficiency，nitrogen use efficiency and water use efficiency under sufficient water conditions.Nitrogen treatment in high water(3000 m3·hm-2，N 120 kg·hm-2)is beneficial to high yield，high quality and the high efficiency of water and fertilizer utilization，and it is the optimum water and nitrogen management measure for the biomass production of switchgrass in Yinbei saline-alkali region of Ningxia.