In order to explore the variation patterns of evapotranspiration and crop coefficient of mountain apples under surge-root irrigation in northern Shaanxi, an experiment with three irrigation regimes including high water (H1, (85%-100%) θf, θf is the field water holding capacity), medium water (H2, (70%-85%) θf) and low water (H3, (55%-70%) θf) was conducted to investigate the effects of deficit irrigation on water consumption and crop coefficient, and the model of evapotranspiration estimation based on leaf area index was established. The results showed that the water consumption in the whole phenological stage of mountain apples in northern Shaanxi ranged from 483.03 to 540.10 mm, and the crop coefficients ranged from 0.35 to 0.38 at the germination stage, 0.28 to 0.31 at the flowering and fruit setting stage, 0.70 to 0.83 at the fruit expansion stage and 0.48 to 0.57 at the fruit maturity stage. The crop coefficient and evapotranspiration under different irrigation regimes varied significantly at the fruit expansion stage, which decreased when deficit irrigation was applied at any stage of the above. The leaf area index of each treatment increased with the increase of irrigation amount. The relationship between crop coefficient and leaf area index can be described by exponential regression, based on which a model for estimating the evapotranspiration of fruit trees was established. The results can provide a technical support for the establishment of surge-root irrigation system for mountain apples in northern Shaanxi.