Aimed at the problem of the thermal error of numerical control (NC) machine tool spindle and servo feed system hindered the raising of machine tool position precision, the thermal deformation of NC machine tool of servo feed system was researched in depth. The results show that the nut friction and bearing friction are the main heat sources of ball screw servo feed system, and the friction heat is alomost proportional to rotational speed of ball screw and axial loading. Hollow ball screw and hollow nut were adopted, which effectively restraines the thermal deformation quantity when ball screw in high speed feeding, and the steady error of servo feed system is diminished.