Abstract: The propagation of infrasound in the atmosphere is modeled. By using a finite-difference time-domain method consist of a dispersion relation preserving scheme in space and a Runge-Kutta scheme in time, an infrasound propagation model is developed. The stratospheric ducted propagation of infrasound in a dissipative, gravitational stratified atmosphere is studied by this model. The simulation result shows that the caustic phenomenon occurs in the reflecting region at the height of the stratosphere, the sound pressure of the infrasound decreases while its energy is focused. Compared to the result of ray model, to make a precise prediction of the trajectory, the full wave solution should be employed.