Abstract: 【Objective】To explore the effects of different concentrations of lanthanum on the antioxidant enzyme activity and the ultrastructure of root cells of Tieguanyin and Shuixian,soasto provide data reference for breeding tea varieties with low lanthanum absorption.【Method】Taking Shuixian and Tieguanyin tea as material to examine the antioxidant enzyme activity and root cell ultrastructure and the localization and distribution of lanthanum in response to treatment with 0.08,0.40,or 1.20 mmol/L La³⁺.【Result】When the lanthanum concentration is 1.20 mmol/L,the superoxide dismutase (SOD) activity of Tieguanyin roots is 73.9% higher than that of Shuixian tea,and the peroxidase (POD) activity and catalase(CAT) activity are significantly lower than that of Shuixian tea roots. Scanning electron microscopy observation results showed thatunder the treatment of high concentration,the cells were arranged loosely,irregularly,and have morewax. Compared with different varieties,Shuixian tea had more waxy coverage,more severe damage,and weaker tolerancethan Tieguanyin root cells did. Transmission electron microscopy observation results showed that the root cells of the two tea plant varieties under high concentration of lanthanum scattered irregularly,the cell walls were enlarged,and more black sediments could be found on the cell walls. According to energy spectrum analysis,lanthanum was found in the black sediment,which was mainly distributed in the protoplast of Tieguanyin root cells,and accumulated in the cell walls and protoplast of Shuixian tea root cells.【Conclusion】After lanthanum treatment,the antioxidant enzyme activity of Tieguanyin root was higher than that of Shuxian tea,and the Tieguanyin tea root cell ultrastructure was damaged less,and Tieguanyin tea was less affected by lanthanum. Thus,Tieguanyin teacan be used as a material for breeding lanthanum low absorption tea varieties for in-depth research and development.