Abstract: Hydro viscous dynamometer (HVD) is a key equipment used in the dynamic experiment on vehicle transmission and it's dynamic mathematic model is necessary for the improvement of electro-hydraulic control system of the HVD. An identification was performed to get the dynamic model of hydro viscous dynamometer on the basis of Hammerstein method. At first, a linear subsystem model was identified in the traditional way, then a second order memoryless Hammerstein model was applied to correct the linear subsystem model to coincide with the nonlinearity in real HVD. Thus, a whole dynamic model of HVD was finished. This method was proved by experiment result.