This paper presents object-based segmentation of optical flow field and its motion estimation method. A major difficulty in estimating general motion is that it requires a large area of support in order to achieve a good estimation. Unfortunately, when the supporting area is large, it is very likely to have multiple moving objects. Thus, object-based segmentation and general motion estimation are interdependent problems. To solve the-problem, we propose a multi-stage segmentation method which groups progressively the flow field into segments according to a hierarchy of motion models. The basic idea is to group uniform subregions with respect to a simple motion model Into uniform regions with respect to a complex model using region growing technique. By the method, we can segment the flow field into several parabolic patches. For head-and-shoulder images, simulation results show that it can segment the flow held into meaningful regions such as head and shoulder.