Abstract: To analyze the biotoxicity of radioactive nuclide ¹³⁷Cs and ⁹⁰Sr, liver cells of cynoglossus semilaevis(HTLC) were exposed to DMEM-F12 with a series of concentrations of ¹³⁷Cs and ⁹⁰Sr, respectively.MTT assay was used to evaluate the cytotoxicity of ¹³⁷Cs and ⁹⁰Sr.Lactate dehydrogenase (LDH), reactive oxygen species (ROS) and superoxide dismutase (SOD) activity were applied to explore the oxidative damage of ¹³⁷Cs and ⁹⁰Sr on HTLC.The results indicated that cell activity was significantly promoted by both ¹³⁷Cs and ⁹⁰Sr, especially under their low concentration (p < 0.01), but the promotion was increased first and decreased later with the increase of ¹³⁷Cs and ⁹⁰Sr.The cell membrane was damaged significantly only with low concentration of ⁹⁰Sr (p < 0.05), while ¹³⁷Cs made no damage on HTLC cell membrane.ROS contents displayed significant difference at the lower ¹³⁷Cs concentration and all the ⁹⁰Sr exposure groups (p < 0.05), whereas SOD activity displayed significant difference in all ¹³⁷Cs and ⁹⁰Sr exposure groups (p < 0.05).The results confirmed that ¹³⁷Cs and ⁹⁰Sr was not significantly toxic to HTLC in the environmental activity, and HTLC was able to adjust itself to maintain normal physiological function.However, ⁹⁰Sr can induce oxidative stress in HTLC and damage cell membrane, which may affect the metabolic pathways and lead to potential toxicity in HTLC.