With the recent advancement of C-arm angiographic techniques in acquiring the 3D rotational angiography, the system has the ability to reconstruct the CT-like transaxial slices of the scan volume, but at lower image quality compared to those reconstructed from standard CT system. For liver imaging, the scan time can range from 5 to 10 seconds to complete the halfscan coverage for soft tissue imaging protocol. The lengthy scan time could lead to significant motion artifacts in the reconstructed images such as those found in the liver due to respiration motion. In this paper, we employ the 4D NCAT phantom with a realistic model of the respiratory motion to simulate the movements of hepatic artery, liver and other organs. With a physics based x-ray projection simulator, the projection image sequence of the rotational C-arm angiography is generated. Then, a cone-beam filtered backprojection method is employed with the Shepp-Logan Alter to reconstruct the simulated C-arm CT angiography data. As shown in our simulation results, we are able to study the effect of respiratory motion on abdominal C-arm CT angiography images as well as digital subtraction angiography by using the realistic 4D NCAT phantom, projection and reconstruction tools.