Objective To investigate the protective effect of erythropoietin (EPO) encapsulated in poly (L-lactic-co-glycolic acid) (PLGA) microspheres on damaged retinal ganglion cell (RGC) by intravitreal injection after optic nerve crush. Methods Adult SD rats were selected to establish an optic nerve crush model. Immediately after the crush, the animals received intravitreal doses of 10 IU EPO of EPO-PLGA microspheres (EPO-PLGA group), 10 IU EPO (EPO group), blank PLGA microshperes (PLGA group), and PBS (PBS group) or untreated (untreated group). Five days and 2 weeks after crush, apoptotic RGC were detected with TUNEL labeling in frozen retinal sections.Twenty-three days after optic nerve crush, retinal ganglion cells were retrogradely labeled by injecting DiI into the superior colliculi of the brain. The animals were scarificed 4 weeks after the crush. Mounted retinal photographs were assessed for the number of surviving RGC. Six rats were prepared from each group at every time point. Results TUNEL-positive cells could be identified in all groups 5 days and 2 weeks after the operation. However, there were fewer in both the EPO-PLGA and EPO groups. Retinal mounts revealed that the density of RGC was (2387.7±164.9)cells/mm2 in normal adult rats, and (748.3±58.8)cells/mm2 in the untreated group, (1296.7±157.6)cells/mm2 in the EPO-PLGA group, (1418.5±154.9)cells/mm2 in the EPO group, (821.7±52.1)cells/mm2 in the PLGA group, and (804.4±86.4)cells/mm2 in the PBS group 4 weeks after the operation. Compared to the untreated group, the EPO-PLGA and EPO groups showed a significant neuroprotective effect on RGC (P＜0.01), and no significant differences were found between these two groups (P=0.065).Conclusion The protective effect of EPO-PLGA microspheres on RGC is equal to EPO, which provides evidence for further study on the long-term neuroprotective effect of EPO-PLGA microspheres.