Because the grating scale copying belongs to precision machining, so under the working status the requirement of flatness of the platform which grating ruler is putting on is high. Main structural deformation will happen when it is under the action of weight and compaction force, which affects the machining accuracy. A certain type of long grating precision lithography copy machine is considered as the research object. The finite element method is introduced to the structure improvement. Solidworks is used to establish the three dimensional model of objects and then ABAQUS is used to execute static analysis and modal analysis to existing structure so that weaknesses can be found. Structure improvement can be carried out based on the analysis result, so the stability of the whole structure and the uniformity in the flatness of the display platform can be improved.