Abstract: Taking one-year-old ‘Ruiyang’ apple saplings as the test materials, the effects of different concentrations of calcium and magnesium concentration gradients(Mg0-0 mmol·L^-1 MgSO₄,Mg2-2 mmol·L^-1 MgSO₄,Mg6-6 mmol·L^-1 MgSO₄,Ca0-0 mmol·L^-1 CaCl₂,Ca5-5 mmol·L^-1 CaCl₂,Ca15-15 mmol·L^-1 CaCl₂) on the growth and development, photosynthetic pigment and photosynthetic characteristics of young apple trees were stuided, in order to provide a reasonable basis for scientific fertilization in orchards in the future.The results showed that, 1) under magnesium deficiency treatment, the leaf veins of apple saplings remained green and the veins were degreen.Compared with the normal treatment, the plant height of young trees decreased significantly by 41.5%,the root activity decreased significantly by 46.6%,the contents of chlorophyll a, chlorophyll b and carotenoids in leaves decreased significantly, the chlorophyll content decreased by 49.9%,and the net photosynthetic rate in leaves decreased significantly by 51.7%.2) Under high magnesium treatment, leaf margin curled and leaf back bulged.Compared with the normal treatment, the plant height decreased by 28.3%,and the chlorophyll b content in leaves decreased by 16.2%.3) Under calcium deficiency treatment, the leaves of young apple trees showed brownish yellow chlorotic spots and premature senescence.Compared with the normal treatment, the plant height and stem diameter of young trees were significantly reduced, and the root activity was significantly reduced by 76.6%.At the same time, chlorophyll a, chlorophyll b in leaves were significantly decreased.In terms of photosynthetic characteristics, the net photosynthetic rate of leaves was significantly decreased by 74.6% compared with that of the normal treatment, and the stomatal conductance and transpiration rate were decreased by 47.9% and 36.4%,respectively.4) Under high calcium treatment, the leaf edge of young trees was brown withered and the leaf edge ruptured.Compared with the normal treatment, the plant height was significantly reduced by 37.3%,and the chlorophyll b content in leaves was significantly decreased by 28.9%.In summary, under calcium and magnesium deficiency stress, the growth and development of fruit trees were slow, the ability of root to absorb nutrients was poor, the leaves became green and yellow, the chlorophyll synthesis was blocked, and the photosynthetic intensity was reduced.However, the effect of excessive calcium and magnesium stress on young apple trees was less than that of calcium and magnesium deficiency treatment.