Interface temperature is an important factor of sliding failure. In this paper, the simplified problem of calculating the transient temperature in a sliding asperity contact is studied with dimension analysis. By considering the effects of surface film and the distribution of heat source intensity, an approximate formula, which is used to calculate the transient hot spot temperature of a mixed lubricated sliding asperity contact, is proposed. Focusing on the fact that almost all failure of sliding contacts is accompanied by plastic deformation of asperities, the applicability of "Blok Flash Temperature" theory, the critical velocity and the critical PV criteria are researched with stress analysis. In addition, the effect of surface film loss on plastic deformation of asperities is discussed simultaneously by using the approximate formula proposed in this paper. The results show that the difference between the "Blok Flash Temperature" theory and the experiments is dependent on the geometric character of asperities, the external pressure and the velocity. Finally, the applicability of the temperature criteria is studied.