There have been many problems such as deterioration of the disk and burn out of the friction material in the wet clutch, due to the multi-stage, size-reduction and high torque of the automatic transmission. The deterioration and burn out of the clutch disk causes a great loss in the quality and performance of the transmission and it is one of the major quality problems. In order to prevent such quality problems, it is necessary to analysis clutch heating and cooling performance precisely. In this study, the supplied lubricant flow rate of each element in automatic transmission was analyzed. And we have developed the heating and cooling analysis technology of the transmission wet clutch that reflects the actual 3D shape and operating conditions.