Optimum n-drift region of a 4H-SiC Junction Barrier Schottky Diode (JBS) was analyzed by simulation with consideration of the anisotropic impact ionization. According to the detailed simulations using SRIM and Sentaurus, model parameters of empirical equations were obtained through fitting, which showed that the anisotropic avalanche model (2D-ANISO) differs significantly from the 1-dimensional empirical model (1D-Cooper) and the old isotropic avalanche model (2D-ISO). These initial results suggested that the JFET resistance and anisotropic impact ionization should be taken into account during the optimization of a 4H-SiC JBS in which field crowding at the corner of p-grid causes higher reverse leakage current.