Acute Ischemic Stroke (AIS) is the major type of stroke occurring in patients. Aspiration thrombectomy, which uses suction to remove the thrombosis, is a promising technique in the clinical treatment of AIS patients. In this research a computational fluid dynamics (CFD) analysis was conducted to model the blood flow dynamics in a simplified cerebral model during an aspiration thrombectomy procedure. The flow system being analysed was a typical in vitro cerebral flow model, and the system parameters were set based on the clinical and in vitro data reported in open literature. The simulated flow field features showed good correlation with the in vitro response as reported in literature. The CFD study provides detailed technical data including the peak velocity occurring at the catheter tip and the suction force-suction distance relation during the aspiration thrombectomy procedure, which are useful new knowledge and have the potential to influence future catheter design as well as clinical operational protocols used during thrombectomy intervention.