In engineering, a sudden impact motion may cause the lubricant to be trapped between two contact pairs, which will have a significant influence on the elastohydrodynamic lubrication (EHL) contact. In this work, a mixed lubrication model of a ball and a plane under pure impact motion is established, which takes into account the dynamic process of impact motion, the elastic deformation, the rheological properties of lubricants, the squeeze effect, etc. The accuracy of the proposed model is validated through comparisons with existing literature. The changes in the contact characteristics during the impact motion are discussed in detail. The effects of lubricant viscosity and pressure-viscosity exponent as well as surface roughness on the impact EHL contacts are studied. The simulation results show that the shape of trapped oil not only depends on the initial impact height, but also on the rheological properties of the lubricant. Choosing an appropriate lubricant can reduce the pressure during the impact motion. In addition, when the roughness is greater than 0.05, it will hinder the formation of trapped oil phenomenon.