In the present study, we detected the level of oligomeric form of alpha-synuclein in the red blood cells of ischemic stroke, Parkinson's disease, and normal people and compared the differences to assess the diagnosis potential of alpha-synuclein in ischemic stroke patients. 86 ischemic stroke, 100 PD, and 102 healthy cases were enrolled in the present study. Total protein amount in the red blood cells were quantified by BCA assay using spectrophotometer. Levels of oligomeric form of alpha-synuclein were characterized by a sandwich ELISA. Analysis of correlation analysis and receiver operating characteristic curve were conducted. Significant differences were detected in the levels of oligomeric forms of alpha-synuclein in different samples' blood cells (P < 0.05); the levels of total protein in (188.1 +/- 33.9 mmol/L) healthy people were significantly higher than that of PD (147.7 +/- 45.0 mmol/L) and ischemic stroke groups (142.9 +/- 43.0 mmol/L) (P < 0.05). There was no correlation between the age of patients and level of alpha-synuclein (R-2 = 0.216 in ischemic stroke group and -0.104 in PD group) and the receiver operating characteristic curve analysis showed a high sensitivity of alpha-synuclein in discriminating ischemic stroke (sensitivity was 63.7 % and specificity was 9.6 %) and PD (sensitivity was 44.1 % and specificity was 12.5 %) patients from the controls. The levels of oligomeric form of alpha-synuclein of red blood cells in ischemic stroke and Parkinson's disease patients were both significant higher than normal people. And the level of oligomeric form alpha-synuclein showed a potential for diagnosis of ischemic stroke in clinic.