Heavy rain in southwest of South China caused by typhoon "Durian" is simulated by MM5. Based on the excellent agreement with the observation,the area average energetic budgets and conversion over the region of typhoon is undertaken with the balance equation of kinetic energy for the divergent wind and rotational wind,to indicate the maintaining mechanism of typhoon and the characteristic of evolution of energy,as well as the relationship between the typhoon and its outside enhanced heavy rain.