Abstract: In terms of the accelerated wear of the screw raceway due to mixed lubrication in the low-speed operating ball screws, an elastohydrodynamic lubrication (EHL) contact model of ball screws based on the isothermal EHL theory was proposed to study the friction mechanism and wear form between the ball and raceway. First, the raceway surface geometric model based on the Frenet-Serret coordinate transformation method was established. Subsequently, the EHL contact model of ball screws based on the Reynolds equation was proposed, and the distributions of the film contact stress, film thickness, and asperity contract stress were determined. Finally, the friction mechanism of ball screws was clearly elucidated from a microcosmic perspective, which was composed of the asperity contact friction coefficient and the oil film lubrication friction coefficient. Results show that the wear forms of screw raceway are adhesive wear and abrasive wear, and the simulated friction coefficient curve trend agrees well with the classical Stribeck friction curve trend, which accurately identifies the friction coefficient and lubrication status of ball screws under different screw speeds based on the measured friction torques.