Considering the soil water deficit and low water use efficiency of apple orchards in the semi-arid areas of Northwest China, the effects of mulching and water supply on growth, physiological properties and evapotranspiration features of columnar apple trees were investigated to explore suitable irrigation depth and soil water conservation measures for healthy growth and higher water use efficiency of apple trees. The weighing bucket experiments under a shelter were subjected to four irrigation water levels: 60%ETC (W1), 80%ETC (W2), 100%ETC (W3) and 120%ETC (W4), and two mulching modes: mulching (M) and no mulching (NM), resulting in eight treatments in total. The results showed that dry matter was increased with the increase of irrigation amount, and the M treatment promoted accumulation of dry matter. Net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) were increased with the increase of irrigation depth. Pn and Tr at different growth stages under different irrigation depths and mulching modes showed a decreasing trend as fruit enlargement stage, fruit maturation stage, flowering and fruit bearing stage and leaf changing stage. Under the same irrigation depth and mulching mode, Pn, Tr and Gs at different times in a day showed a decreasing trend as 10:00, 13:00 and 8:00, 13:00, 10:00 and 08:00, and 10:00, 08:00 and 13:00, respectively. The maximum and minimum leaf water use efficiency (LWUE) found at 10:00 in the MW2 treatment （4.52μmol/mmol） and at 13:00 in the MW4 treatment （2.62μmol/mmol）, respectively. The accumulative evapotranspiration during the whole growth period was increased with the increase of irrigation depth, those of NM treatments were increased by 11.02%~16.35% compared with those of M treatments. Water consumption rate at flowering and fruit bearing stage, fruit enlargement stage, fruit maturation stage and leaf changing stage reached 3.29~4.36mm/d, 2.40~4.85mm/d, 0.83~1.79mm/d and 0.77~1.53mm/d, with the corresponding water consumption modulus of 19.34~27.40%, 55.99~61.41%, 8.62%~12.63% and 5.85%~7.24%, respectively. The results indicated that the W4 and M treatments were beneficial for improving the growth and physiological characteristics of columnar apple trees, but the highest water use efficiency was obtained in the W2 treatment. Fruit enlargement stage was found to be the most active physiological metabolic reaction stage of columnar apple trees, and mulching played a certain role in the soil water conservation.