A toolpath topology design method based on vector field in sub-regional processing for the curved surface is disclosed which comprising: finding the functional relationships in feeding direction between the chord error and the normal curvature and between the scallop-height error and the normal curvature; establishing the bi-objective optimization model and calculating the optimal feeding direction at each cutting contact point within the surface through the constructed evaluation function, the space vector field is built; calculating divergence and rotation of the projected vector field and according to whether them are zeros or not to classify different sub-regions, the primary surface segmentation is achieved, etc. The method is applied for the complex curved surface processing, which can reduce the machining error and enhance the feed motion stability.