For the advantages of efficiently energy-saving and stepless speed regulation, hydro-viscous drive (HVD) has been widely applied in many industries, such as farm machinery, fuel power, metallurgy, petrochemical, and so on. Traditional design of hydro-viscous drive always uses the friction pairs of damp clutch indiscriminately. But now, this method to design friction pairs cannot meet the practical engineering application. Based on the correlative theoretic analysis and experiments, this paper studied the method of how to design the friction pairs especially for HVD.