WRF-Fire consists of a fire-spread model, implemented by the level set method, coupled with the Weather Research and Forecasting model (WRF). In every time step, the fire model inputs the surface wind and outputs the heat flux from the fire. The level set method allows submesh representation of the burning region and flexible implementation of various ignition modes. This presentation will address the numerical methods in the fire module, solving the Hamilton-Jacobi level set equation, modeling real wildfire experiments, and visualization.