To study the ischemic stroke risk factors in spontaneous internal carotid artery dissection (ICAD) patients via analyzing the dissection features and primary collateral circulation using vessel wall-MRI and magnetic resonance angiography.ICAD patients who had undergone VW-MRI were included in this study. A total of 36 patients were included and divided into ICAD stroke (N = 23) and non-stroke (N = 13) group. Dissection imaging features [intramural hematoma (IMH), length of IMH, intimal flap, double lumen, intraluminal thrombus, degree of stenosis] and primary collateral status were analyzed. The primary collateral score (0-4) was evaluated based on presence of anterior communicating and ipsilateral anterior cerebral artery A1 segment (0-2) and ipsilateral posterior communicating artery (0-2).There were no significant differences in dissection imaging features such as presence of double lumen, intimal flap, IMH, length of IMH and intraluminal thrombus between the two groups. Degree of stenosis and primary collateral score showed significant differences between the two groups.Both the poor primary collateral circulation and severe stenosis may play an important role in occurrence of ischemic stroke for spontaneous ICAD patients and good primary collateral circulation can help to reduce the incidence of infarction.ICAD is one of the major causes of ischemic stroke. Early evaluation of the status of the Circle of Willis in ICAD patients by MRI may help to make treatment strategies and improve clinical outcome.