Purpose-To study plasma homocysteine(Hcy)/D-dimer levels in patients with differernt subtype of acute cerebral infarction for early etiology diagnosis. Methods: The subjects were 246 acute cerebral infarction patients in the first 24 hours of stroke onset at our hospital. We divided them into large –artery atherosclerosis(LAA) group(n=66), small artery occlusion(SAO) group(n=76), cardio embolism(CE) group(n=40),stroke of other demonstrated etiology(SOE) group (n=11)and stroke of other undemonstrated etiology(SUE) group(n=51) according to the TOAST classification. Plasma homocysteine and D-diamer were determined within the first 24 hours of admission, the differences in subgroups and control group(n=121) were analyzed. Results : Plasma homocysteine levels in LAA group were signficantly higher than other groups( P <0.05), no differences in non-LAA groups( P >0.05);Plasma D-diamer levels in CE group were significant higher than other groups( P <0.05), no differences in non-CE groups( P >0.05). Conclusions: Plasma homocysteine and D-diamer level are associated with subtypes of acute cerebral infarction, and it contributed to early classification diagnosis and individual treatment of patients with acute cerebral infarction.