Background: Intracranial atherosclerotic stenosis (ICAS) is a major etiology of stroke worldwide, especially in East and South Asia, accounting for up to 50% of all ischemic stroke. Previous three randomized clinical trials did not demonstrate the superiority of intracranial stenting over aggressive medical management for symptomatic intracranial atherosclerotic stenosis (sICAS). The SAMMPRIS and VISSIT trials demonstrated that aggressive medical management was superior to self-expanding stenting and balloon-expanding stenting for sICAS. The CASSISS trial showed no significant difference in the risk of stroke or death between self-expanding stenting and aggressive medical management for sICAS. But recent BASIS trial demonstrated that balloon angioplasty plus aggressive medical management, compared with aggressive medical management alone, lowered the risk of a composite outcome. CRTICAS was a prospective, real-world registry with 26 participating centres. It demonstrated a lower complication rate in treating patients with symptomatic ICAS with endovascular therapy in a real-world context, compared with the preceding RCTs. Uneven development in endovascular technology, institutional experience and patient selection in different volumes of centres may have an impact on overall safety of this treatment. The patients were screened from December 2013 to December 2015, which was almost 10 years ago. In consideration of the development of imaging evaluation and interventional devices, the CRTICAS-2 aims to figure out the effect and safety of endovascular treatment plus medical management for sICAS patients nowadays. Methods: As a multicenter and prospective cohort study, it starts in December 2024, the observation is scheduled to be completed by December 2028, with a total of at least 1000 sICAS patients recruited. The information on clinical, radiological, and laboratory practices will be recorded objectively. All of the patients will be monitored until death or 12 months after the occurrence of symptomatic stroke. Study Design: In this study, an observational cohort will be set up. The primary outcome is the effect of endovascular treatment, which is subject to assessment using the total mortality and symptomatic stroke. The second outcome is the safety of endovascular treatment, with the postoperative ischemic complication. Based on the observation of the characteristics and outcome of sICAS patients, the ischemic events after surgery will be further addressed, and the function assessment system for operated sICAS patients will be established. We will detailedly collect the clinical data of all patients registered for the study includes medical record data; imaging examination; laboratory examination; hemodynamic evaluation and cognitive function evaluation. The imaging examination includes Magnetic Resonance Imaging(MRI), High-Resolution Magnetic Resonance Imaging(HRMRI), Computed Tomography Angiography(CTA), Magnetoencephalography (MEG) , Ultrasound and so on. The hemodynamic evaluation includes Optical CoherenceTomography (OCT), noninvasive FFR estimated from Phase Contrast Magnetic Resonance Angiography (PC-MRA) and so on. The cognitive function evaluation includes cognitive domains of verbal episodic memory, semantic verbal fluency, confrontation naming, mental processing speed-attention, executive function-cognitive flexibility and so on. Objective: To observe the effect of endovascular treatment plus medical therapy in patients with symptomatic intracranial atherosclerotic stenosis.