The prediction of temperature distribution and variation of oil-cooled sliding disk pair is essential for the design of wet clutches and brakes in vehicle transmission system. A heat transfer model is established in the study and some fluid-solid coupled heat transfer simulations are performed to investigate the thermal behaviors of wet clutch during sliding. Both cooling liquid and grooved solid disks are contained in the heat transfer model and the heat convection due to the cooling liquid in the radial grooves is also considered by fluid-solid coupled transient heat transfer simulations. The temperature distribution and variation of the grooved disk are discussed and analyzed in detail. The results indicate that the temperature distribution on the grooved disk is nonuniform. The temperature within the middle radius area is higher than that in the inner and outer radius area. The outer radius temperature is higher than the inner radius temperature at the contact face. The subregions which divided by the radial grooves show similar temperature distribution. The temperature besides the groove in each subregion is not symmetric and the higher temperature occurs at the area near the leading edge. On the symmetric plane, the similar asymmetric temperature distribution can also be found. The average temperature on the contact plane and symmetric plane increases almost linearly after the starting stage and the temperature difference between the two planes becomes larger with increasing time. The study results of sliding friction pair can be used in temperature control and cooling device design for wet clutches and brakes.