In order to establish the hydraulic design process of the torque converter, pump, turbine and stator were designed by reverse design method including one dimensional analysis, angular momentum distribution and forced vortex design. And the significance of evaluation of the circulation flow rate in torus of the torque converter was verified by numerical calculation if the combined blade rows of pump and turbine. It was confirmed that the computational method using interrow mixing model by Park and Cho was reliable to predict the flow-field and performance of the torque converter.