The situation and progress of the domestic and foreign research on hydrodynamic transmission in recent years were summarized. It includes the CFD numerical simulation of the inner 3D flow in hydrodynamic transmission elements, the characteristic prediction based on the numerical solution of the 3-D flow field, and the experimental study on the inner complex flow in hydrodynamic elements by means of the advanced flow measurement technique, such as particle image velocimetry (PIV). Finally, the further research directions were put forward as follow: blade design based on 3-D flow theory and transient characteristic study of the flow field.  