Poncirus trifoliate L. was used to be treated with normal calcium (1.23 mmol/L) and deficient calcium (0 mmol/L) levels. The hydroponics results showed that deficient calcium treatment reduced the root biomass and the extraction rate of root cell wall. The activities of antioxidant enzymes (SOD,CAT,POD,APX) decreased by 31.96%,71.27%,35.91% and 45.70%,respectively. Calcium deficiency significantly decreased total calcium,cell wall calcium,chelated pectin calcium and alkali-soluble pectin calcium in root. Among which,the content of chelated pectin and alkali-soluble pectin in root cell wall decreased by 35.16% and 40.51%,respectively. Results of XRD analyses showed that calcium deficiency had little effect on the crystallinity of cellulose in root cell wall. Under deficient calcium condition,the activities of antioxidant enzymes and the content of pectin in root cell wall decreased dramatically,resulting in the loss of the ability of cell wall to resist calcium deprivation and the failure of cell wall to maintain its normal function,thus seriously hindering the growth of trifoliate rootstock root.