Abstract: Ion optic system（IOS） is one of the critical subassembly of ion thruster（IT）.It’s performance directly affects the IT performance.Grid is important component of the IOS.The structure of it is perforated thin plates with convex.Finite element model of grid subassembly is established by ANASYS software based on homogenization method.The analysis of the modal,the displacement and the resonance under uniform load of grid subassembly is carried out.The results offer useful information for design,manufacture and assembly of grid subassembly.