The cerebrovascular spasm is a common complication of subarachnoid hemorrhage. The prognosis is affected severely with regard to quality of life of patients, and earlier determination of the cerebral vasospasm becomes very important. In recent years, there have been many research results in early judgment of cerebrovascular spasm, and imaging technology research is particularly prominent in this area. This article summarizes the advantages and disadvantages and the specific roles of several common imaging technologies to determine the early stage of cerebral vasospasm. Transcranial Doppler (TCD) was the first used to examine cerebral vasospasm and mainly detected vascular hemodynamic changes of cerebrovascular spasm in patients. Digital subtraction angiography is the gold standard for diagnosis of cerebral vasospasm, but its efficacy in determining severity of cerebrovascular spasm indexing is still in dispute. It is invasive, it is difficult to repeat the examination, and it can induce complications, so its clinical application is limited. CT imaging technology is a hot topic in this area. There is an important guiding significance in early diagnosis and treatment of cerebral vasospasm in CT perfusion imaging (PCT) and CT angiography (CTA). PCT mainly performs qualitative and quantitative analysis through hemodynamic parameters such as cerebral blood flow, cerebral blood volume, and mean transit time. CTA is minimally invasive, fast, and reliable as an efficient imaging technology, and will possibly replace DSA for the assessment of vasospasm, particularly in critically ill patients with cerebral vasospasm in an urgent examination. This means it has greater value and helps to improve the prognosis of patients. MR imaging in the early stages to judge cerebral vasospasm has great value. DWI can effectively assess the cerebral vascular spasm earlier to detect trace bleeding sites and reflect the damage of cerebral vasospasm by apparent diffusion coefficient. Combined with DWI and PWI, perfusion can be understood in all regions and can be found in ischemic penumbra, which is a more accurate way to determine cerebral vasospasm and more beneficial in guiding the treatment of patients and improving their prognosis. However, there have been false-negatives and false-positives when detecting cerebrovascular spasm post-SAH. It is of great importance to select accurate, convenient, non-invasive imaging technologies that judge cerebrovascular spasm and guide treatment that improves the prognosis of these patients and other aspects.