With barrel planted red Fuji apple saplings as test materials,experiments which had four levels of irrigation(W₁ ,sufficient irrigation; W₂,mild water stress; W₃,moderate water stress; W₄,severe water stress.The lower and upper limits of irrigation were 75%—90%，65%—80%，55%—70% and 45%—60% field capacity,respectively) and three levels of fertilization( F₁，higher level; F₂,medium level; F₃，lower level.The N,P₂O₅ and K₂O were 0.6，0.2，0.2 g/kg，0.4，0.2，0.2 g/kg and 0.2,0.2,0.2 g/kg,respectively) were conducted to study the effects of water and fertilizer coupling on growth,photosynthetic characteristics and water use efficiency of two-year young apple tree under the drip irrigation.The results showed that compared with F₃W₄ treatment,F₁W₁treatment increased plant growth and leaf area by 85.2% and 74.5% respectively,while F₁W₂treatment increased plant growth and leaf area by 98.7% and 87.3% respectively,which indicated that the combination of high fertilizer and mild water deficit (F₁W₂treatment) was most conducive to the plant and leaf growth of young apple tree. The maximum val ues of water use efficiency occurred in F₁W₂treatment at each growth stage(germination and flowering stage,new growth stage,fruit setting and expanding stage and maturation stage) and were 3.49,3.84,4.37 and 3.90 mmol/mol，respectively.Meanwhile，compared with F₁W₁,although the net photosynthetic rate decreased by 1.9%,7.2%,6.8% and 2.1% respectively,the water use efficiency increased by 5.8%，6.7%，4.5% and 3.2% respectively,which indicated that the moderate water deficit could im prove the water use efficiency of young apple trees.Moreover,the maximum differences of net photosyn thetic rate and transpiration rate of apple saplings under different treatments all occurred in the fruit set ting and expanding period,which indicated that the fruit setting and expanding period of young apple tree was the most critical period of water and fertilizer demand,during which reasonable regulation of water and fertilizer could promote the growth of young apple trees．