Film boiling has many applications in various industries, which heat exchangers are among them. To this end, film boiling simulation to study heat transfer on a flat surface, the behavior of the liquid-vapor interface, and the growth of bubbles is very important in the industry. Front tracking film boiling simulation with finite difference discretization on a horizontal plane with a constant boundary flux in the two-dimensional model is presented and the governing equations for both phases are going to be solved separately. Also, the terms regarding viscosity, surface tension, and inertia have been considered. By changing the viscosity, the changes of dimensionless Grashof number was investigated. The changes in the Nusselt number with time were investigated for different Grashof numbers and the simulation continues until the changes in Nusselt number with time are almost constant. The effect of dimensionless capillary number on the Nusselt number and bubble deformation was investigated. Keywords: Film boiling on a flat surface-constant heat flux-front tracking meth