In radiotherapy treatment planning, tumor segmentation has a great significance. However, tumor volumes and anatomical structures are manually contoured for dose calculation, which takes time for physicians. The purpose of the study is to describe a new and automated method for generating contours. A few high curvature points are manually drawn on a CT slice. Then Fourier interpolation is used to complete the contour. Consequently, a deformable image registration method based on ‘optical flow’ is used to map the original contour to other slices. This technique has been applied successfully to contour anatomical structures and tumors. And the difference of the volume and the geometry center between the generated contours and the original contours is in the accepted range.