AIM: To observe the protective effect of human umbilical cord mesenchymal stem cells (hucMSCs) on retinal ganglion cells (RGCs) injury in mice with acute ocular hypertension (AOH). METHODS: Fifty-six adult male C57BL/6 mice were randomly divided into four groups: normal group, AOH group, hucMSCs group, normal saline (NS) group. Left eye of mice was induced by 90 mm Hg intraocular pressure for 1h to establish AOH model. hucMSCs 1×105/μL, 1 μL or NS 1 μL was injected into the vitreous body the next day. CM-Dil fluorescent dye was used to label the 3rd generation of hucMSCs, for tracing the cells in the vitreous cavity of mice. Seven days after the model established, hematoxylin-eosin (HE) staining was used to observe the thickness of the inner retina layer in four groups. Numbers and loss rate of RGCs were evaluated by counting Brn-3a positive cells stained by immunofluorescencein. RESULTS: On the 7th day after AOH established, labeled hucMSCs were found in the vitreous cavity. HE staining showed that the thickness of retinal inner layer in AOH group was significantly lower than that in normal group and hucMSCs group (P<0.05), same as that in NS group (P>0.05). Compared with AOH group, the RGCs in normal group was significantly higher; RGCs number increased in hucMSCs group and the loss rate was lower (P<0.05). Injection of NS had no protective effect on RGCs. CONCLUSION: In AOH mouse model, vitreous injection of hucMSCs have shown a protection for RGCs.