Pitch accuracy is one of the main indexes of screw form grinding because its accumulated error plays a decisive role in the positioning accuracy of ball screw. The great amount of heat produced in grinding is conducted into the workpiece through the grinding contact area proportionally, which causes the axial thermal elongation of screw and then deteriorates the screw pitch accuracy obviously. Based on some simplified conditions, the finite element method was used to do transient thermal analysis on temperature field of screw. The infrared thermal imager was utilized to establish the experiment system for screw temperature measurement in grinding process. According to the thermal imagines of screw, the influence of machining parameters on the temperature distribution and thermal elongation of workpiece at different time in dry grinding was analyzed, which was helpful to ensure the pitch accuracy of ball screw.