Abstract: Computer numerical control (CNC) precision vertical grinder has the advantages of less deformation and better roundness during processing. It is widely used in the grinding field of sleeve, disk, ring, small table and other parts in the machine tool industry. Compared with foreign countries, domestic machine tool industry in the field of high-end grinding machine has low production efficiency, poor machining accuracy and other problems. In this paper, with a type of CNC precision vertical grinding machine as the research object, first of all, through the study of motion relationship between the key components, the corresponding geometric error parameters were obtained, and then parts were built based on multi-body system theory, the transformation matrix between the grinding machine precision machining constraint equation was obtained, and thus space of the grinding machine geometric error model was established. Based on the spatial geometric error model, the error sensitivity model was established, and the key error terms affecting the machining accuracy were obtained. Finally, the key error items were repaired to complete the machining accuracy optimization of CNC vertical grinder, which can provide a theoretical basis for the design of vertical grinding machine.