To explore the effect of different concentration of calcium on yield，quality，enzyme activity and leaf calciumcontent of pakchoi in different growthstages，and to determine the optimal application amount and period of exogenouscalcium in pakchoi，using Suzhou Green，Rabbit Ear White and Shanghai Green as experimental materials，six calciumsupply levels[water control(T 0)，50 mg/L CaCl 2(T1)，100 mg/L CaCl 2(T2)，150 mg/L CaCl 2(T3)，200 mg/L CaCl 2(T4)，250 mg/L CaCl 2(T5)]were sprayed on the leaves of pakchoi at7，14 and 21 days after transplanting in the fieldtest.The effects of different concentrations of calcium on enzyme activity，calcium content，yield and quality of pakchoiwerestudied.The results showed that there were significant differences incatalase(CAT)andperoxidase(POD)amongdifferent varieties of pakchoi treated with different concentrations of exogenous calcium in different periods，the activitiesof the two enzymes both increased first and then decreased with the increase of the spraying calciumconcentration，andthe enzyme activity reached the maximum in the T3treatment，and the CAT and POD activities increased by 79.33%and114.05%，respectively，compared with the control in 14 days aftertransplanting.With the increase of calciumconcentration，the content of calcium increased significantly in different spraying periods and varieties of pakchoi，and spraying calcium on the 14thday of transplanting had the greatest impact on the calcium content of the leaves，and the impact on the 7thday after transplanting was the least.At the same time，different varieties showed Shanghai Green>SuzhouGreen>Rabbit EarWhite.The content of V C，solublesugar，free amino acid in leaves of pakchoi could be increased byspraying calcium on the surface of leaves and nitratedecreased.Compared with thecontrol，the content of V C，soluble sugar and free amino acid in different varieties of pakchoi in different spraying periods increased the most in T3treatment，with thehighest increase of10.91%，3.94% and10.82%.After 21 days oftransplantation，the content of nitrate in T 3 of Rabbit EarWhite treated with calcium was thelowest，which was 9.09% lower than that of thecontrol.Spraying different concentrationsof calcium significantly increased the calcium content of pakchoi，and with the increase of calcium concentration showed atrend of increasing first and then decreasing，T 3treatment was the maximum.After 21 days of transplanting，the yield ofShanghaiGreen，Rabbit Ear White and Suzhou Green increased by4.86%，3.09% and3.83%，respectively.Appropriateapplication of exogenous calcium can improve the enzymeactivity，quality and yield of pakchoileaves.Spraying 150 mg/L CaCl2 after 21 days transplanting was the best application period and dosage for spraying calcium on the leaves of pakchoi.