The characters of C-V model are analyzed in this paper. Using the C-V technique to segment objects from an image, every pixel of whole image needed to be updated in each iterative calculation. The amount of iterative calculation is very large. So a computational method combine C-V model with the narrow band of level set is proposed. The segmentation iterative computation is defined on a narrow band, so the computation complexity is gotten lower. This segmentation algorithm is simulated in MATLAB. The simulation results shows that this segment arithmetic is efficiency, constringency fast and can get object integrally.