Background Unclippable fusiform basilar trunk aneurysm is a formidable condition for surgical treatment.The aim of this study was to establish a computational model and to investigate the hemodynamic characteristics in a fusiform basilar trunk aneurysm.Methods The three-dimensional digital model of a fusiform basilar trunk aneurysm was constructed using MIMICS,ANSYS and CFX software.Different hemodynamic modalities and border conditions were assigned to the model.Thirty points were selected randomly on the wall and within the aneurysm.Wall total pressure (WTP),wall shear stress (WSS),and blood flow velocity of each point were calculated and hemodynamic status was compared between different modalities.Results The quantitative average values of the 30 points on the wall and within the aneurysm were obtained by computational calculation point by point.The velocity and WSS in modalities A and B were different from those of the remaining 5 modalities; and the WTP in modalities A,E and F were higher than those of the remaining 4 modalities.Conclusions The digital model of a fusiform basilar artery aneurysm is feasible and reliable.This model could provide some important information to clinical treatment options.