The positioning accuracy of ball screw is highly lowered by the thermal deformations of ball screw, with ball screw is an important module of machine tool servo feed system. Meanwhile, the thermal deformations of ball screw are also the bottleneck of the highspeed and highprecision development of machine tool. However, the hollow ball screw with cooling oil system is a breakthrough solution to the problem. The positioning accuracy of hollow ball screw was affected by following factors: the axial load, the rotation rate, the type of cooling medium, velocity of flow of cooling medium and the inner diameter of the hole of hollow ball screw, all these factors not only had influence on cooling, but also on deformations of hollow ball screw greatly. The study results show that axial load and rotation rate have little influence on temperature. Special cooling oil is more suitable for cooling the ball screw, and rationally controlling its temperature rise and thermal deformations. The optimal inner diameter of hole is given by analyzing thermal defromations and heatstructure coupling, which has a theoretical significant value on the design and the study of hollow ball screw.