Abstract: Objectives　To study the influence of Staphylococcus epidermidis (SE) on the neonatal mice of different ages. Methods A total of 60 neonatal mice including postnatal day 1(PND1) and postnatal day 3(PND3) were divided into SE group, normal saline (NS) group and control group, with 20 mice each. Mice in SE group were intravenously injected with 50 μl SE (108/ml). Mice in NS group were given 50 μl NS and mice in control group was not intervened. On postnatal day 14, the brain, liver and spleen obtained from mice were weighted. Serial sections of paraffin-embedded brain tissue were used for the detection of microtubule associated protein-2 (MAP-2) and myelin basic protein (MBP) by immumohistochemical staining, and then the areas and volumes of grey and white matter were calculated. Result The mortality of PND1 mice in SE and NS group was 60.0% and 40.0%, respectively, and there was no difference between two groups (P>0.05). The mortality of PND3 mice in SE and NS group was 10.0% and 0.0%, respectively, and there was no difference between two groups (P>0.05). There were no differences in body weight, body weight gain, spleen and liver weights and organ coefficient between PND1 and PND3 mice (P>0.05). In PND1 mice, the areas and volumes of grey and white matter were significantly smaller in SE group than those in NS group (P<0.05). However, in PND3 mice, there was no differences in areas and volumes of grey and white matter between SE and NS group (P>0.05). Conclusions SE infection can result in brain injury in PND1 mice, but has no effect on brain tissues of PND3 mice.