Abstract: Composite grid method（CGM)uses the idea of domain decomposition algorithm.In CGM，the computed domain is divided into two regions，and used two separate mesh grids:one coarse for the global region and one fine for the local region.In electromagnetic scattering problems，the finemesh region includes the information of fine structure.Used the connected boundary conditions，the coarse mesh and the fine mesh are separately calculated.The iteration continues until the results converge.The electromagnetic scattering information of the fine structure can be obtained.In this paper， the 2D model containing one thin wire is researched.From the results， CGM can reduce the amount of calculation，and shows good agreement with the regular finite element method.