Any model merely simulates a approximate status of atmosphere.Considering that the model is traditionally supposed to be exact and only initial data fields are amended in Adjoint Assimilation System(AAS).In this paper,the MM5 Adjoint Assimilation System is used to correct MM5's terrain error.The experimental results of amending different initial terrain data indicate that:the MM5 AAS is able to retrieve the terrain field,whose resolution is matched with one of the initial meteorological element field and therefore well coordinated with the MM5 model.Thus a new way about how to widely use the assimilation system is offered in this paper.