Objective To observe the effects of tetrandrine on ultrastructure of cultured rabbit conjunctival fibroblasts(RCF) and the retinal toxicity.Methods Cultured fibroblasts were exposed to different concentration of Tetrandrine solution (2,4 mg·L -1 ).Ultrastructure of RCF were investigated by electromicroscope after exposed to tetrandrine for 48 hours.Fifteen healthy rabbits were divided into 3 groups randomly.Different concentration (300,600 mg·L -1 )of tetrandrine were injected intra-vitreous body and 0.1 mL saline was also injected as control.Retinal toxicity were examined by electroretinogram(ERG) and visual evoked potential(VEP)at the third and fourteenth day after injection.Results Ultrastructure of RCF had no change after exposed to tetrandrine 2mg·L -1 48 hours,but the number of secondary lysosome increased and showed myelinated structure after exposed to tetrandrine 4mg·L -1 48 hours.ERG and VEP had no significant difference between control group and(300 and 600 mg·L -1 )tetrandrine groups before and after intra-vitreous body injection 3 days(P>0.05),but markedly reduced after 600 mg·L -1 intra-vitreous body injection 14 days(P<0.000 1).Conclusion Tetrandrine has cytotoxicity for the growth of RCF but low dose concentration of tetrandrine is safety for inhibit proliferation of rabbit conjunctival fibroblasts and clinical use.