Abstract: ‘American Celery’ was used as the test material, the effects of different calcium concentrations(0.5,1.0,1.5,2.0,2.5 mmol·L^-1) on the calcium content, photosynthetic characteristics and yield quality of celery was investigated by hydroponics, and the optimal calcium concentration for hydroponics celery was selected, in order to provide reference for the high yield and quality of hydroponics celery.The results showed that the calcium content of celery leaves and petioles was enhanced with the increase of calcium concentration.With the increase of calcium concentration, photosynthetic pigment, net photosynthetic rate（Pn）,transpiration rate（E）,stomatal conductance（Gs）,plant height, stem diameter and fresh weight of celery leaves were increased first and then decreased, and the highest value was reached at 1.0 mmol·L^-1 calcium concentration.The contents of quality indicators including total phenols, vitamin C,free amino acids and soluble protein in celery leaves and petioles were also raised and then lowered with increasing calcium concentration, and the highest contents were found under the treatment of 1.5 mmol·L^-1 calcium concentration, which were increased by 41.92%-325.65% and 27.47%-170.89%,1.13%-21.10% and 1.92%-22.21%,30.01%-38.95% and 43.46%-82.16%,38.72%-125.82% and 9.86%-568.57%,respectively, compared with other treatments.In conclusion, 1.0 mmol·L^-1 calcium concentration treatment was beneficial to increase the yield of hydroponic celery, and 1.5 mmol·L^-1 calcium concentration treatment was beneficial to improve the quality of hydroponic celery.