In order to improve the precision and stability of high precision CNC machine tools, by starting from the study of improving the transmission structure of screws which had the greatest influence on the precision and stability, a new screw precision prestretching method was studied to solve the defect of positional accuracy. This defect was caused by the problem that other screw prestretching method could not precisely control the amount of bar pretension which might make the screw roller track deformation could not meet the design value and ultimately could not accurately offset the amount of thermal deformation in the screw thermal deformation and finally it mighe influence the positional accuracy. This precision prestretching technology is easy and simple to handle with high level of stability and controlling the stretching amount. This technology can be widely used in all kinds of transmission structures of highprecision CNC machine tools and can effectively improve the positional accuracy and stability of the precision of entire machine tool.