Abstract: The thermodynamic process within screw vacuum pumps directly reflects its performance, holding significant research value. This study focuses on two types of screw vacuum pumps, analyzing the thermodynamic parameters including pressure, temperature, internal energy, and enthalpy of gas based on adiabatic, polytropic, and isothermal processes. The correlation between exhaust temperature and suction pressure for constant and variable pitch screw vacuum pumps was calculated. Additionally, the distribution of temperature, pressure, and deformation of rotors was analyzed through numerical simulation. The calculations indicate that as the suction pressure increases, the exhaust temperatures initially decrease slowly and then rapidly. For the variable pitch screw vacuum pump, the exhaust temperature remains constant after over-compression; the order of exhaust temperature at the same suction pressure is adiabatic, polytropic, and isothermal processes. The numerical simulation gives more accurate results for covering the effect of leakage and backflow, with higher temperatures and pressures than theoretical calculations. Deformation simulation indicates that bending is a significant factor affecting the deformation of the screw rotors, with constant pitch rotors being more prone to bending. The deformation pattern of the screw rotor obtained from numerical simulations can be verified in practical engineering.