Coil embolization using a micro catheter and coils is one of the most popular surgical methods used for treating intracranial aneurysms. Surgeons need to better understand the effects of changing catheter position because this is under their control during operations. In this study, we simulate coil embolization for a basic bifurcation-type aneurysm using finite element method and computational fluid dynamics. We evaluated the reduction in velocity after embolization and the distance of the embolized coil's center of gravity from the center of the aneurysm (rCG) while changing the catheter tip position. The results show there is a high correlation between velocity reduction and neck volume embolization ratio (NVER) with a correlation coefficient of 0.955, and between the catheter tip position and rCG with a correlation coefficient of 0.866. These results indicate the NVER is also important for effective velocity reduction in both bifurcation-type and sidewall-type aneurysms. In addition, it is useful to set the catheter tip at the bottom of the aneurysms to deploy the first coil as a framing coil.