Rational water and fertilizer management have an important impact on alfalfa production. This research aimed to explore the effects of water and phosphorus (P) fertilizer on hay yield, nutrient quality, water-use e ciency (WUE) and phosphorus-recovery e ciency (PRE) of each cut of alfalfa under drip irrigation and to determine the best water and P interaction model for high quality and yield of alfalfa. In this study, different irrigation levels, i.e., 5.25, 6.0, and 6.75 ML ha -1 (referred to as W 1 , W 2 , W 3 , respectively), and P fertilizer levels (0, 50, 100, and 150 kg P 2 O 5 ha -1 referred to as P 0 , P 1 , P 2 , P 3 , respectively) were set to determine the hay yield and nutrient quality of each cut of alfalfa under drip irrigation and to calculate WUE and PRE. The hay yield of each cut of alfalfa increased rst and then decreased with increased P fertilizer under the same irrigation amount, and there was no signi cant difference among different irrigation treatments with respect to the hay yield of alfalfa. The crude protein (CP) reached a maximum under the W 2 P 2 treatment. WUE decreased gradually with an increasing irrigation amount under the same P application. The WUE of alfalfa increased rst and then decreased with the increase of P application under the same irrigation amount, and WUE was 0.20%-4.75% (2016) and 1.31%-6.22% (2017) higher in the P treatments than in the non-phosphorus treatments. PRE decreased gradually with increasing P application under the same irrigation amount. Therefore, we conclude that moderate irrigation (6.0 ML ha -1 ) and P fertilizer (100 kg P 2 O 5 ha -1 ) combined with application, the alfalfa has higher WUE and PRE, and can signi cantly promote the alfalfa hay yield and nutrient quality of each cut.