Objective Simulate the blood flow numerically in patient-specific cerebral aneurysms and help assessing the risks of rupture and reoccurrence of cerebral aneurysms in clinic. Methods Geometrical models were constructed from three-dimensional rotational angiography data, Herschel-Bulkley non-Newtonian fluid model was chosen for the blood, and the commercial CFD software was employed to simulate the blood flow in the two patient-specific computational models. Results The streamlines, the velocity fields in important cross sections, the wall shear stress distribution and total pressure distribution on the aneurysmal wall were obtained. Furthermore, the graphs of wall shear stress and total pressure, at 20 points of the neck and top of each aneurysm respectively, at systolic time, were plotted. Conclusion Hemodynamic factors play important roles in the growth and rupture of cerebral aneurysms and patient-specific CFD simulation of blood flow in cerebral aneurysm can make a contribution in studying the hemodynamics in cerebral aneurysms. Distribution of wall shear stress is different from that of unsteady index of wall shear stress at the neck of the aneurysm, and the relationship between the oscillation of wall shear stress and the risks of rupture and reoccurrence of the aneurysm should be studied.