Abstract: In order to study the thermal deformation law of the grids assembly of the ion thruster,and analyze the effect of different aperture ratio and aperture methods on the thermal deformation of the grid.The full size finite element model of the grid assembly is established using shell elements,body elements and beam elements respectively.The results show that the grid thermal deformation is centrally symmetrical and as the aperture ratio increases,the thermal deformation of the grid decreases.Moreover,the influence of different aperture methods on the thermal deformation of the grid is very small when the aperture ratio is constant.