Based on the FLUENT user defined function dealing with the boundary moving and mass-flow-inlet in the buring surface of propellant, considering the pressure and flow velocity on the erosion effect, the transient internal flowfield in a bore-burning solid rocket motor was studied. The integrational chamber-nozzle internal flowfield was simulated using standard k -e turbulence model and implicit coupling algorithm. The ballistic parameters changes with time and space distribution, dynamic burning process, and the erosion effect on the pressure distribution and working process in a solid rocket motor were obtained.