Objective To investigate the retinal toxicity and verify the safe dose of intravitreal injection of nonsteroid anti-inflamatory drug,diclofenac sodium.Methods Twenty-eight healthy adult white rabbits were divided at random into 7 groups and received in every right eye the intravitreal injection of a single dose of diclofenac sodium solution ranging from 0.4-0.1 mg/0.1ml respectively ,the left eyes were regarded as conreol ones.Before injection and on the 1st,3rd,7th,14th,21st,and 28th day after injection the electroretinography on both eyes was examined.On the 28th day after injection the retinas of two rabbits of every group were examined by using light microscopy.On the 10th and 30th day after injection the retinal tissues around the optic nerve sisk of two eyes from every group at random were tested by using transmission electron microscopy.Results The retio of amplitude ofb wave of electroretinography in 0.4mg and 0.5mg groups had no sighnificant difference from groups before injection,the retinal tissues showed no structural changes in light and ecectron microscopy examination.The ratio of amplitude ofb wave of photoptic electroretinogrphy in 0.6mg groups in the early stage after injection was markedly reduced（P＜0.05）and returned to that before injection with time,reversible change of the edematou retina was discovered.The ratio of amplitude of b wave of electroretinography in 0.7-1.0mg groups was distinctly descreaded after injection（P＜0.05 or P＜0.01）,the cells of all the retinal layer revealed apparent and irreversible damage.Conclusion The largest dose of safety of intravitreal diclofenac sodium should be not more than 0.6mg.The toxic effect of intravitreal diclofenac sodium on retina is concerned mostly to cones and rods.