Abstract: In the modeling of CoPlanar Waveguide (CPW) by a quasi-static Finite Difference Method (FDM), to resolve the problem of too much simulation time with equidistant discretization in the 3D FDM simulation and improve the non-equidistant discretization in the algorithm complexity and efficiency, a new progressive discretization is put forward, which is extremely easy to implement with good compromise of precision and efficiency. And the CPW transmission line, open end and short end are modeled successfully based on the improved FDM. After a special modeling of CPW short end, the progressive discretization is proved to be practicable. At the same time, some particular references are also presented as in some applications.