Gas diffusion in char pores or other fractal pores is anomalous diffusion that does not follow Fick's diffusion law. The authors studied gas diffusion in fractal porous media by simulating molecular movements in porous models. Through analyzing numerical results, gas diffusion equations in fractal pores have been presented. The effects of geometrical structures on pore diffusion can be described by three parameters: porosity, specific surface area, and fractal dimension. With these three parameters, the diffusion coefficient can be calculated. The steady-state diffusion equation is quantitatively determined so that it can be potentially used in modeling char combustion or other practical applications.