In recent years, for patients with acute ischemic stroke due to large vessel occlusion, intravascular mechanical thrombectomy has become the most recommended treatment method. Determining whether there is ischemic penumbra or not is very important for the selection of patients who are suitable for endovascular mechanical thrombectomy. In addition, the ischemic penumbra also provides guidance for extending the time window of traditional intravenous thrombolytic therapy. This article reviews the imaging evaluation methods of ischemic penumbra.