Objective To study the effect of smoking on oxidized low-density lipoprotein ox-LDL lag time in patients with cerebral infarction. Methods Plasma samples were obtained from 67 patients with cerebral infarc-tion. 30 acute cerebral infarction patients without history of smoking were chosen to be as control group; meanwhile, 37 acute cerebral infarction patients with history of smoking were chosen to be as smoking group. There was no statis-tical difference in age,gender,blood pressure,lipid level and location and level of the cerebral focus between the two groups (P > 0.05). The ox-LDL lag time and lipid levels of low-density lipoproteins (LDL), including total choles-terol (TC) ,triglyceride (TG) and free cholesterol were measured. Results The ox-LDL lag time of the patients with history of smoking was significantly shorter than that in the control group[(77.21 ± 9.1) min vs. (59.95 ± 8.7)min,P <0.001]. There were no significant differences in LDL- TC,LDL- TG and LDL-free cholesterol level[(5.12±0.61) vs. (4.63±0.62) mmol/L; (0.89±0.07) mmol/L vs. (0.85±0.04) mmol/L; (1.71±0.43) vs. (1.74±0.91) mmol/L, P > 0.05 respectively] between the two groups. Conclusion Smoking shorts the ox-LDL lag time in patients with cerebral infarction, and decrease the anti-oxidization and increase the stress of oxidization.