Abstract: A comparative study is made between the land and sea monsoon troughs by applying diagnostic balance model, kinetic energy balance equation and energy convertion equatio, ns.For the land trough, the vertical motion associated with non-divergence wind is basic and those associated, with the large scale condensation and cumulus convection heating have large amplifying effects.But for the sea trough, its vertical motion field is mainly maintained by cumulus convection.The kinetic energy generation induced by divergence wind and the subgrid scale effect is the main kinetic energy source for both cases, meanwhile the non-divergence wind cause negative kinetic energy generation.There exists positive baraclinic convertion within both kinds of monsoon trough.