Abstract: The lubricating states of a steel ball-disc point contact pair and a steel sliding block-disc plane contact pair were investigated based on theoretical analysis of the relevant Stribeck curves and thin film lubrication test. Thus the Stribeck curves involving the thin film lubrication regime were obtained by changing the rotary speed of the disc. As the results, it was feasible to recognize thin film lubrication regime on the Stribeck curves, and the thin film lubrication zone was near to the friction coefficient valley. The appearance of the thin film lubrication regime and its range was closely dependent on the surface roughness of the disc. Namely, it was easy for the frictional pair to reach thin film lubrication regime as the disc had a smaller surface roughness, while it was hard to differentiate the thin film lubrication regime as the disc had a larger surface roughness. Moreover, the Stribeck curve for the frictional pair of a smaller disc surface roughness showed a broader frictional coefficient valley and thin film lubrication zone as well.