In this paper, a new model based on variational level set method for segmenting multiphase images is proposed. Its energy functional is based on the level set functions and the regional characteristics functions. It can deal with changes in curves' topology and be extended to multiphase image segmentation models which are based on other schemes for region competition as well. The gradient flow of the energy functional is computed using variational method to get the optimized solution of the model. In order to guarantee more accurate calculation, discrete definition of level set functions is used. Experimental results show that the new model has promising effect on image segmentation.