Abstract: The single head screw vacuum pump, characterized by small rotor clearance and low inter-stage leakage, has become the preferred choice for high-efficiency, "pollution-free" vacuum applications. However, gas backflush at the outlet can induce rotor temperature rise and thermal deformation, potentially leading to rotor seizure. Therefore, it is of significant practical and economic importance to study the temperature field, thermal deformation characteristics, and cooling strategies of rotors. In this study, a 50 L/s single head screw vacuum pump is investigated. ANSYS software is employed to conduct simulation analysis on the temperature field and thermal deformation of the sinistral rotor and the dextral rotor, along with research on cooling methods. The results show that the axial deformation difference between the two rotors is less than 0.025 mm, which has a negligible impact on operation. In contrast, radial deformation is cumulative and must be carefully considered; specifically, the maximum radial deformation is 0.14 mm. Based on this, a reference curve for radial clearance is proposed, providing guidance for rotor manufacturing and assembly. Cooling studies indicate that both purge cooling and axial water cooling are effective in reducing rotor temperature. Moreover, the cooling efficiency of axial water cooling shows a diminishing rate of improvement as the flow rate increases. This work provides valuable insights for optimizing rotor clearance design and cooling system development in screw vacuum pumps.