The hydro-viscous drive (HVD) is an effective device to save energy and reduce consumption. In order to reveal the flow field characteristics and calculate the shear torque, the mathematical model of fluid flow characteristics was built. The characteristics of velocity distribution, pressure distribution and theoretical required flow rate were obtained through the step analytic method. Then cavitation was analyzed based on the Reynolds boundary conditions, and the equivalent radius and shear torque model were achieved. Meanwhile, the equivalent temperature model was introduced by considering temperature field. Finally, the test rig of torque characteristics was set up to testify the trend of fluid field and shear torque. The characteristics of flow field and shear torque during the full film shear stage in HVD can be forecasted much more accurately through both experimental research and theoretical modeling which mainly consisted of equivalent temperature model, equivalent radius model and shear torque model.