Numerical simulation is performed to investigate the flow friction performance of the water-cooled nozzle used in the high speed rod rolling. A great deal of resistance characteristic data are obtained based on a series of numerical computations of flow process in the water-cool nozzle. The research results reveal the effects of the mass flow rate of the water，the diameter and the speed of the rod on the flow friction. The empirical formula is fitted with those computed resistance coefficients. Finally the formula is revised with the measured data from the actual product line，which will provide a theoretical basis for the design of the control cooling technology in the high-speed wire rod rolling process.