In this work, we try to use the so-called Piecewise Constant Level Set Method (PCLSM)for the Mumford-Shah segmentation model. For image segmentation, the Mumford-Shah model needs to find the regions and the constant values inside the regions for the segmentation. In order to use PCLSM for this purpose, we need to solve a minimization proble musing the level set function and the constant values as minimization variables. In this work,we test on a model such that we only need to minimize with respect to the level set function, I.e., we do not need to minimize with respect to the constant values. Gradientdescent method and Newton method are used to solve the Euler-Lagrange equation for the minimization problem. Numerical experiments are given to show the efficiency and advantages of the new model and algorithms.