AIM: To study caspase-9 expression on rat retina in the process of chronic elevation of IOP and the changes with the application of amino guanidine (AG), thus to investigate the potential protective function of AG to rat retina with chronic elevation of IOP. METHODS: Immunohistochemistry, RT-PCR and Western blot were used to observe retinal morphology and the expression of caspase-9 at different time points of rat with chronic IOP elevation, both affected and not affected by the application of AG. ·RESULTS: Compared with control group, as time passed retina of experimental group gradually had detectable morphological changes. On 21^st day of chronic IOP elevation, retinas became thinner and the quantity of retinal ganglion cells (RGCs) decreased; caspase-9 expression increased, consistent with the morphological changes. The group using AG presented relatively smaller morphology changes and less expression of caspase-9. CONCLUSION: Apoptosis-related gene caspase-9 plays a part in the process of chronic IOP elevation; AG protects retina by down-regulating expression of caspase-9.