Objective: To determine the protective effect ofmonosialoganglionside (GM1) and evaluate the influence of GM1 on expression of N-methyl-D-aspartate receptor subunit 1 (NMDAR1) in Sprague-Dawley (SD) rats with focal cerebral ischemia-reperfusion (I/R). Methods: Left middle cerebral artery (MCA) was occluded by an intraluminal suture for 1 h and the brain was reperfused for 72 h in SD rats when infarct volume was measured, GM1 (10 mg/kg) was given ip (intraperitoneally) at 5 min(group A), 1 h (group B) and 2 h (group C) after MCA occlusion (MCAo). Expression of NMDAR1 was detected by Western blot at various time after reperfusion (4 h, 6 h, 24 h, 48 h and 72 h) in ischemic hemispheres of the rats with or without GM1 administered. Results: (1) Adjusted relative infarct volumes of groups A and B were significantly smaller than that of group C and the control group (P＜0.01 and P＜0.05, respectively). (2) Expression level of NMDAR1 was temporally high at 6 h after reperfusion,and dipped below the normal level at 72 h after reperfusion. GM1 at 5 min after MCAo significantly suppressed the expression of NMDAR1 at 6 h after reperfusion (P＜0.05 vs the control). At 72 h after reperfusion, the NMDAR1 expression level of rats treated with GM1 administered (at 5 rain or 2 h after MCAo) was significantly higher than that of the control (P＜0.05). Conclusion: GM1can time-dependently reduce infarct volume in rats with focal cerebral I/R partly through stabilizing the expression ofNMDAR1.