Aiming at the problems of decoupling and analysis of optical flow vectors with various motion states confronted in the pose estimation process of autonomous vehicles (AVs) using optical flow, the optical flow motion field model (OFMFM) is derived and the decoupled optical flow motion filed model (DOFMFM) is analysed as the vehicle poses change independently in six degrees of freedom. According to the DOFMFM, a simulation algorithm is designed for the vehicle platform, and the completely decoupled simulation results are presented. The DOFMFM is applied to quantify and verify the simulation results. Two real scenes of translation and rotation from the KITTI dataset are utilized for the flow-decoupled experiments. The consistency among model analysis, simulation process, real data and comparison results is verified. The results show that the proposed decoupled model analysis, simulation algorithm, simulation and real results together with comparison analysis can not only be applied in the error analysis and algorithm test of pose estimation, but also provide a reference or instruction for the improvement in the understanding of optical flow motion imaging and the research on the optical flow based applications on an AV platform.