Guo proposed an improved CV model （MCV model） that needs less iteration

but trapped in local optima for the influence of regions of initial contours； also some points were segmented in a wrong region or were omitted. The means gated by traditional Heviside function isnt accurate to keep the numerical stability. In this article we modify the MCV model

propose a new model using n equations of level set to structure n Regions： pre-segment the image to get the initial contours to avoid the results trapping in local optima and improve the efficiency of segmentation.Then we modify the MCV model by structuring a new symbol function to replace the Heviside function which can keep the numerical stability. Experiment results show that the new model can obtain good results efficiently.