Objective To investigate the establishment of collateral circulation in patients with massive cerebral infarction caused byacute internal carotid artery (ICA) occlusion and related influencing factors.Methods A total of 29 patients who were diagnosed with massive cerebral infarction caused byacute ICA occlusion were enrolled, and all of them underwent carotid artery ultrasound, transcranial Doppler (TCD), head CT scan, cranial magnetic resonance angiography (MRA), and electrocardiography (ECG). Related information was also collected.Results Establishment of primary collateral circulation was significantly associated with diabetes (P<0.05), but was not associated with atrial fibrillation, hypertension, smoking, and NIHSS score (P>0.05). Establishment of secondary collateral circulation was not associated with atrial fibrillation, hypertension, diabetes, smoking, and NIHSS score (P>0.05). Acute massive cerebral infarction caused by cardiogenic cerebral embolism was significantly associated with cerebral hernia (P<0.05). Establishment of primary collateral circulation assessed by TCD was highly consistent with that assessed by MRA (Kappa=0.656, P<0.05).Conclusions Diabetes can promote primary collateral opening in patients with massive cerebral infarction caused by acute ICA occlusion. Patients with massive cerebral infarction caused by cardiogenic embolism are likely to develop cerebral hernia. TCD is an effective tool forassessing the establishment of primary collateral circulation in patients with massive cerebral infarction caused by acute ICAocclusion.