Objective To investigate the correlation between levels of serum angiopoietin-1 （Ang-1）and the severity of acute cerebral infarction，in order to provide evidences for early clinical evaluation of acute cerebral infarction. Methods Patients with acute cerebral infarction in the Ninth Hospital of Xi’an City were enrolled as the case group. In the corresponding period，healthy subjects in physical examination cen-ter were enrolled as the control group. The general clinical data of all subjects were collected. The levels of serum Ang-1 were measured in all subjects. The patients were divided into three groups according to NIHSS score or maximum infarct diameter in MRI respectively. The difference of clinical data between the case group and con-trol group were analysed. Logistic regression analysis was used to analyse the risk factors. ROC curve analysiswas used to evaluate the diagnostic value of serum Ang-1. Spearman correlation analysis was used to analyzethe correlation. Results The percentages of smoking，hypertension，diabetes mellitus and atrial fibrillation were significantly increased in the case group，while the levels of serum Ang-1 were significantly decreased（P＜ 0.05）. Logistic regression analysis showed that diabetes mellitus and the levels of serum Ang-1 were risk factors of cerebral infarction （P＜0.05）. ROC curve analysis showed that the area under the ROC curve was 0.791 （95%CI=0.751-0.830）about the diagnosis of acute cerebral infarction with the level of serum Ang-1. Significant differences were found between the levels of serum Ang-1 in mild， moderate and severe NIHSS group （P＜0.01）. Significant differences were found between the levels of serum Ang-1 in large infarction，middle infarction and small infarction group（P＜0.01）. Spearman correlation analysis showed that NIHSS score and maximal diameter of infarction in MRI were negatively correlated with the serum level of Ang-1 （r= -0.498，-0.459；P＜0.01）in acute cerebral infarction patients. Conclusions The level of serum Ang-1 in patients with acute cerebral in-farction decreases，which is closely related to the severity of cerebral infarction.