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In order to explore the scientific and reasonable irrigation and fertilization system for apple trees in semi-arid region, the effects of water and fertilizer coupling effect on the growth and physiological characteristics of young apple trees in northern semi-arid region under drip irrigation were studied. Four irrigation levels and three fertilization levels were set, among which irrigation treatment was 75%~90% (W1), 65%~80% (W2), 55%~70% (W3) and 45%~60% (W4) of field water holding capacity. The mass ratios of N, P2O5, K2O to airdried soil were 0.9g/kg, 0.3g/kg, 0.3g/kg (F1), 0.6g/kg, 0.3g/kg, 0.3g/kg (F2) and 0.3g/kg, 0.3g/kg, 0.3g/kg (F3), respectively. The results showed that: under different water and fertilizer coupling treatments, the maximum value of plant growth, leaf area and dry matter weight of young apple trees at each growth stage appeared in F1W2 treatment, and the minimum value appeared in F3W4 treatment. Compared with F1W1 treatment, plant growth and leaf area were increased by 6.9%, 6.2%, 11.0%, 2.7% and 9.3%, 5.8%, 5.0% and 3.3%, respectively, at germination and flowering stage, shoot growth stage, fruit setting and maturity stage. The growth index could reflect the physiological characteristics of crops to some extent. With the growth of the trees, different water and fertilizer coupling treatments had more and more influence on the SPAD value of apple trees-leaves. Water consumption of apple trees during the whole growth period was increased with the increase of irrigation amount and fertilizer amount. Water productivity of apple trees under F1W2 treatment reached the maximum of 2.43kg/m3, and increased by 14.6% compared with that of F1W1 treatment and water consumption was decreased by 12.2%. The maximum value of net photosynthetic rate, transpiration rate and stomatal conductance of young apple trees appeared in F1W1 treatment, and that of F1W2 treatment were decreased by 4.2%, 9.7% and 4.2%, respectively, but water use efficiency was increased by 5.9%, and the maximum value also appeared in F1W2 treatment. In conclusion, F1W2 water and fertilizer treatment reached the best water and fertilizer coupling mode and was the best irrigation and fertilization system.